They can't bomb road that far from near Poland. Even if the Russian bomber take off in Belarus, there are still around 500km of hostile ground to cover and lacking of stealth fighter, that's too dangerous to cross into Ukraine and bomb target that far west in Ukraine, you would have to run into a lot of SAM and fighter interception. Had Russia achieve complete Air Superiority, that would be another question. But seeing they just have their Su-35 and their general shot down in a Su-25. It is safe to conclude Russian Air superiority is far from being achieve.
Missile do not have enough CEP to hit railway or road (I don't think any country on earth can be that accurate enough to be able to hit a road)
Same thing with Railway, you can only bomb what you can, in this war, a lot of destruction were done on Artillery, not Air Power. Which mean unless you are within range of that artillery circle (25km) anything beyond that is untouched.
RuAF is not USAF, what the US will do is to neuter your airforce first, either on the ground or on the air, and then push SEAD mission to take out your SAM, then you have Air Superiority and then it is where the B-52 come in. Russia, or one reason or the other, had not done that as explain before, they even have fighter jet and bomber being down by Ukrainian air defence recently.
Again, the only way to reach anything outside artillery range is missile, and Russia don't really have that many missile to begin with. Once they are expanded, it's gone. Unless RuAF start challenging Ukrainian Air Superiority, you are not going to see anything being touch outside that 25 km artillery range.
A better question should be why RuAF did not challenge Ukrainian Air Defence, they have the number, and presumably the skill to do so, but they didn't do so, I don't believe Ukrainian Air Defence is that good that Russia cannot penetrate. That would be the better question to ask, because without that, unless you have unlimited amount of missile supplies, You can only support within your artillery range.
It's quite clear on the first month of war Russia cannot support a war from Belarus front logistically. They tried by taking the road and taking Hostomol Airport, but that log train is just too long and too prone to get ambushed. That is why they withdraw from that axis to begin with.
That IMO is the only thing Russia did right. With that amount of troop (roughly 100,000) and without Air Superiority, you can't supply "Multiple" front. It will take away your supporting asset and you lose concentration. 100,000 troop may seems a lot but considering Ukraine have at least 8 Brigade with unknown TDF Brigade in the area, (that's 50,000 +) 100,000 is the minimum you need in order to pull off an offensive. Traditionally you need 3 attacker to overwhelm 1 defender.
Even when Russia sort of try to go in with multiple axis, the Izyum and Popasna axis have not moved any at all in the last month. As I said, instead of going after Sieverodonetsk, if I am the Russian, I will try to break out from these two city, because that is the only way I can encircle the Ukrainian troop and force them to fight a set piece which I know I can win.
Now instead of a set piece, I have in my hand a urban city fight, which just a grinding battle. For what? A city in Luhansk? After that, I would have to fight another city, then another, then another...............
That's the problem, they don't.
Images show the charred remains of the aircraft believed to be shot down using an anti-aircraft missile in the Kharkiv region.
www.ibtimes.sg
Russia’s Su-35 fighter jet has been shot down by the Ukrainian fighter aircraft over Kherson Region. â Ukrinform.
www.ukrinform.net
Kanamat Botashev, a 63-year-old major-general who volunteered to return to service, awarded the posthumous title of ‘Hero of Russian Federation’.
www.scmp.com
THIS is the dramatic moment a Russian helicopter explodes into a fireball as it’s struck by a Ukrainian missile. The aircraft was downed in the Donbas region of eastern Ukraine, where much of…
www.thesun.co.uk
Ukrainian defenders have shot down Russia’s Su-25 aircraft over the city of Orikhiv, Zaporizhzhia Region. â Ukrinform.
www.ukrinform.net
Set aside whether or not these Russian aircraft were actually being shotdown (even tho A lot of them comes with video evidence) that show Ukrainian Air Activities is quite active.
There are 3 different level of Air Superiorities.
1.) Dominant Air Superiority - Your enemy fly, your enemy dies, you can intercept every single sorties your enemy launches
2.) Complete Air Superiority - Your enemy have capability to fly, but not the capability to challenge you.
3.) Partial Air Superiority - You have achieve a localise air exclusion zone, you can challenge every air traffic in that zone
At this point, what Russia have is either 3 or is still contesting air superiority. The Sky is free for Ukrainian to fly on, and they did challenge Russian Air Force in just about every corner in Ukraine. Again, that is just from the activities level, I am not talking about actually shooting down Russian Aircraft.
And without either 1 or 2 (most likely 1 to minimize lost) you really cannot hit anything outside that Artillery range
Well, I don't think Ukrainian Air Defence is depleted. First of all, Russia did not flew enough sorties to make it happen, You degrade your enemy air power by flying into their area and challenge them, say what you will, but Russia did not use much of its air force since the war, and for a country like Ukraine, Russia would probably have to up their air activities 10 times or more to be able to deplete Ukrainian Air Superiority.
EDIT:: Let me give you a comparsion. DoD Estimated that Russia few 320 sorties between Feb 24-March 20, that's almost a month, 320 sorties. US Air Force flew 100,000+ sorties from Jan 17 to February 23. in the first gulf war to completely decimate Iraqi Air Defence.
The air war is changing over Ukraine. Russia has increased its number of sorties but appears to be running low on precision-guided munitions.
www.airforcemag.com
What Russia is doing now is like waiting on Ukrainian Air Defence to rust or somehow exploded by themselves. I mean, the only way you can degrade their air capability is by go in there and kill them, and Russia didn't exactly go in there, let alone killing them. Missile barrage is ineffective to taking out Ukrainian Air Defence. Missile does not have enough payload to "level" an airfield, and you need precise intel to strike localised air defence. But then as I explained before no country in the world can have that amount of CEP on launching a cruise missile and hitting a say S-300 air defence system....That is just too small of a target to be hit by cruise missile.
Now this war are 2-D, without Air Power, you will not be able to break Ukraine behind your line. That is why the progress is slow, because you can move quick without air cover.
So the question is, why RuAF did not get in there and finish the job. Pretty sure Russia Air Force have enough unit to patrol Ukraine 24/7 and impose a no fly zone, that, by all account, both Russian and Ukrainian, did not happen.