My theory:

I think it used to be that the customers for Unreal Engine oftentimes weren't all these big studios at all. The only AAA games I personally remember from late 2000s and early 2010s that used UE, other than Epic's own games of course, were the Mass Effect games.

Now they've got investors to please (Tencent) so they keep pushing new features that look great in showcase trailers, for big studio execs to pick Unreal. And it seems to be working. Downside is that these things need to be used really carefully or sometimes not at all, but they're advertised as the end-all-be-all solution to make things pretty and easier to build. I'm talking about Lumen, Megalights, Nanite, etc.

E.g Nanite makes little to no sense for games where all your scenes are low complexity. You'll just lose a bunch of performance. It starts making sense when you have a lot of complex geometry and then it boosts how much you can actually do at the top end. Not every game needs it.