Yes, it's been a thing for at least a decade, I imagine it helps with pre-sales online, though it may just be offered as a convenience. It really does help keep the movie from unexpectedly being a lousy experience; if you're stuck in a crappy seat, or your family can't sit together, it's because you picked those seats. As someone else mentioned, it also allows them to bring you dinner and provide that upsell as well.

Even our small independent theater in town has reserved seats, some of which are couches.

I've never been to a theater without assigned seats. Maybe it's a regional difference?

When I grew up in LA 20+ years ago, seating was way more casual. Now everywhere seems to want assigned seating. I think this is in part because so many theater chains now offer a "premium" dining experience. It's yet another reason I rarely go to theaters anymore, on top of most of the film offerings being crap.

It’s the only way I’ve ever seen movie tickets sold outside of North America anywhere.

I feel like the newer (e.g. post 2010s) theaters with more "premium" comfortable seats tend to assign seats these days. Probably differs by chain.

Yes for higher end theaters like imax and the kind where everyone had a recliner chair