1.) plants can carry insects and parasites
2.) snakes destroy most plants when they are crawling around at night (maybe not as hatchlings but DEFINITELY as adults)
3.) Fake plants are cheap and if you go to a craft store you can get some really awesome real looking one's for faily cheap...
As a quick sidenote, my ball python somehow unscrewed my red bulb out of the socket in his 70gal acq. (I have home made-in tank fixtures). The bulb was found next to his stone house and wasn't shattered (I don't know how it wasn't broken). She must have latched on to it and brought it down...
Snakes can and will be as mischevious as possible...