The water temp has to be perfect. Plus it can be stressful. Unless you have a chubby or eggbound female, there really is no reason to do it.
Edited to add...what if your snake gets stressed, thrashes and injures himself? Or (heaven forbid) you forget and leave him in there and he drowns? Or the water is too cold and he gets a resp infection? Or the water is too hot and he gets burned?
I know I sound like a paranoid nut, but bad things can happen so if it is something that is more of a risk than a benefit to my critters, I tend not to do it.