I think its just human nature to want to interact with their pet. Mostly all the responces here have been trying to put human emotions with the reptiles when thats just not the way it is. We would love to think our reptiles love us... but there is no real way to prove or disprove it. I say its best left up to each individual (I can also vouch for corn snakes and leos knowing your voice though... my voice stimulates almost all of my pets in fact... both the vertebrates and invertebrates)
Does a reptile NEED to be handled... no way. Does a reptile LIKE to be handled? Hard to say... I haven't learned how to talk to the animals yet
BUT When I handle a snake and its not heaving for breath or acting frightened (ie. biting, hissing, trying to run away from me) I interpret that as the snake TOLERATING me. I do think they enjoy the body warmth... I have worn a ball python like a bracelet for the span of 2 or 3 hours (granted, this was a very placid and well-behaved specimen)
The only time I would say handling is MANDATORY is if you are trying to keep a specimen "friendly" (educational shows, zoos, etc.) We all know that they become accustomed to being handled and seem to no longer see us as a threat. Even my ultra-hostile texas rat snake has calmed down now and let me handle him without a fuss when I had to move him to his new tank (this was a snake that used to strike madly at me anytime I was within 6 feet of his cage!)
For this reason I could see a pet shop owner telling their employees that its important to handle the reptiles... after all, its a lot harder to sell a beardie that hisses and bites than it is to sell a beardie that sits in your hand and smiles right?