i only handle mind like twice a week, once for feeding, once for cleaning him out.
i think that handling not only benefits the snake but benefits the owner too. The owner has to be used to handling the snake, know how to handle it, knowing its "personality" and how it reacts to certain things. that way the handler will know if it has a tendency to bite them or it may slither off under the floorboards, stuff like that. i know that after not handling any of the larger species for a while, i was quite nervous when i had to handle some of the big snakes at work a few weeks ago.
i also think that it provides them with some other sort of stimuli, instead of: log, newspaper, waterbowl, hide... just my 2p