I still use it and I'm well over 30. I can't speak to your friends, but I like the history of where I've been. I love driving and finding new places -- at least, back when things were open, remember when there were cafés and stuff? -- and, on the flip side, I (used to) go out to eat for most meals and could fall into regular patterns, and sometimes checking Swarm to remind me that, yes, I
had been to such-and-such place twice already this month could kick me into trying something new.
Making the coins utterly useless irritates me, though, and I'm kind of surprised they dropped the whole notion of partnering with businesses to offer specials to regular customers they had in the pre-Swarm days. While I presume they pivoted into selling location data because the partnerships just didn't make them enough money, I'd hope the partnerships weren't losing them money, and I think they really drove usage.