usually the yeshivas that let smoking fall into two categories. either they are very yeshivish, and the result of banning smoking is having a 35 yo mashgiach having to nebach run around trying to bust guys, because no-one will care about any rules; or b. a yeshiva for bochurim that need a little more breathing room (pardon the pun) and have fared badly in the mainstream places. these guys cant deal with rules and people makng them nuts for what really isnt a big deal.
and keep the dumb “well, if their dead blah blah blah” answers to yourself. theyre dumb.
agav, most guys grow out of it.