in winter it's cold and humid inside, they just suck in general to be in. one of the reasons you see infantry riding on top of them is because they're so uncomfortable inside, although this has been claimed to be due to anti tank mines. nah, the dudes know that the tin cans they're riding to war at best protects against a kalashnikov 7.62 round and everything else is going to rip right through, at mines will snap something akin to a btr into pieces no matter where you are. a bmp isn't going to fare much petter honestly.
Finland