I'm at home now so I dont have my books in front of me for the numbers, but it's in the fire codes section of the general building code (try section 15 I think).
I've done a very few installations where an insurance company required pull stations. They were allowed there because the buildings were considered pre-ordinance so not subject to the high rise act (1974).
The argument is that pull stations were the cause of most false alarms. When they eliminated the false alarms they could respond to fire alarms with the whole army instead of wasting time sending a batalion chief out to verify a fire. At least thats what I heard. Either way, it's enforced.