In warfare you gotta use whatever types.Are TSK really need a medium tank for them? Because Cheaper to make and deploy in conflict in syria maybe? Also for stopgap for altay?
Btw as i know kaplan didnt have amphibious capability
Turkey may not have deserts or jungles but the Turkish soldiers still train for these types of terrain.
With your weapons they gotta work in any terrain does not mean Turkish soldiers will fight in jungles.
But its all about being prepared also same with many weapons. War is quite complex you have weapon designs that will work and become the standard or some will fail.
Medium tanks are still being used as they compliment Heavy Tanks.
Light tanks are mainly obsolete due to technology also changes in warfare as Heavy Tanks and Medium tanks surpass them in armour along with speed.
Light tanks mainly suited ww1 and ww2. Some countries may be using light tanks those countries are basically still using ww2 era stuff.