Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
I think everybody who cares about wild trout should belong to TU and I cannot see why they wouldn't. That may make me a little militant, but there it is nonetheless..
If you have a chapter or two in your area you should attend some meetings to see what they are about Every local chapter is different.
I was a member forty years ago. I don't fish any local waters in PA that might have clubs associated with a specific stream so I have no interest. I live in PA and our fish commission does a lot to improve streams.