I quit using straps years ago, when an ex-patroller (turned anesthesiology doc) mentioned that most injuries he'd seen were thumb injuries caused by straps. He didn't use them.
You can wear straps in a way that avoids thumb injury, and I've tried it, but I also like getting off the lift and skiing away. (When my wife skis with me, though, I wait politely while she puts on her straps.) It's never a problem. I don't tense, particularly — I grip with my thumb and index finger as a ring, and use other fingers for control. If I traversed more, I might appreciate straps. Otherwise, no.