It's not necessary for snakes the way it's necessary for lizards that will get MBD without it. But there's good evidence that it provides modest benefits, and it certainly doesn't hurt as long as it's appropriate amount and the animal is able to choose its exposure level. If nothing else, they most likely can see it (especially crepuscular species), so they might as well have it to look at.
I have UV bulbs in my ball python's cage. I have seen him basking openly under them, but more often I see him "cryptic basking" - where he's mostly in a hide but some part of his body sticks out into the light. Of note is that at one point the bulb burned out and it took me awhile to replace it. While it was out, he'd basically always be completely hidden during the day. When I replaced it, he went back to spending most of the day in the hide that's under the light, and always with some loop of his body sticking out. He'll shift positions from time to time, so it's not always the same part of his body. But he usually has some part sticking out under the light. He doesn't do that if he's elsewhere in the cage. He has five other hiding places/burrows, so it's not like he's forced to hang out where the UV is, but he usually does choose to do so.
In any case, it's really not a big deal to replace a bulb or two every six months for one or two cages. And the light looks nice and helps the plants. It's obviously way less important than good hides and proper temps/humidity, but if it's an easy thing I can do that improves my snake's quality of life a little and also make the cage look nicer, why not?
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