IMO...
If you ask a Health expert, they will tell you to wash your hands after handling any type of animal. But, I had three rabbits for a while, almost never washed my hands (my bad) and never got sick. The answer to your question that I would give you is that it's always possible, while very unlikely. You can get other diseases from snakes as well, even though it's, again, unlikely. I would say if it's really that much of a hassle, just get a hand sterilizer so it the process is quicker. Also, I would ALWAYS sterilize after handling a new snake, because you never know what it could have and you might give it to your other snakes or yourself. Also, feeding time is deffinately another time you should wash. As for simple handling of snakes you'd had, it's up to you. (Actual, it's all up to you, but that's besides the point...)