1. They don't care (which is bad, I mean there is big corruption in Iran and regular army isn't trusted so much, same goes for most Arab states or even Russia)
AND/OR
2. they can't, both don't speaks for Iranian leadership.
PS:
As a whole, in the end, Iran is in the long term better prepared, Iran has it's proxies all around Israel and even people who their militias and allies fight in Syria are their useful comrades when it comes against Israel.
I have to admit, Israelis have a great sense of humor.