The doors on a T8 actually sit into a slot on each side panel so I wouldn't be too worried about a cat. Now if you are prone to leaving the doors cracked then you might have issues. The only time I ever had a snake almost escape was a time then I accidentally didn't close the doors all the way.
I think it should be said that if you have an AP cage with the swing doors and not the sliding glass or sliding acrylic doors the locks are much more important.
I always get locks on my cages, but that is to keep other people out and not to keep snakes in. OsirisRa32 has a good point about how high off the ground the cages can be and the locks do add a extra layer of security which is always good. I do think though that as long as you remember to close the doors all the way a BP inside won't be able to get the door open. The locks do force the doors all the way closed, but just like you have to remember to close the doors all the way you have to remember to lock the doors.