I was the only one of my friends who didn't go to prom, and I told them that I thought it was a waste of my time to spend an evening with people I didn't intend on spending much, if any time with once I had left school. I don't regret making that choice. I also didn't go on the primary school trip to france which I also thought was a waste of money and I didn't see what relevance it would have to my education. I don't regret making this choice either.
I think what stands out for me is that I've always been given the choice. I've never brought home a letter and heard my mum say 'well that's something I'll have to start saving for', she's always just asked first whether I even want to go. I then weighed up the benefits of doing something against what I would normally do and then made a choice. No pressure to ever go to things that I didn't want to go to.
I think that what probably happens with most kids is that their parents just assume that they will really want to go so they can just be like everyone else. Fortunately I've never been one to care if I'm like everyone else
If they'd encourage difference and maybe even a bit of rebellion in their kids, they'd probably find that their kids would be less likely to want to even go on the trips and stuff.