The defeat stuff is a kink thing that seems fairly prevalent. People also usually want the meta agency to get their character in a defeat situation, but being forced into it without the player giving their input can be vexing, even for people that want their character to be violated. The defeat system provides a decent setting for the defeat kink and it gives the player the choice of whether they want to lose and get into it or fight and get on with the story/to the next scene. It also provides the excuse that it's an actual game, rather than a "mere" VN where you just pick your choice. Often a waste of time, since many H-RPGs rather suffer from the poorly slapped on RPG aspects of the gameplay, but it artificially adds play time/other stuff that can be advertised and it doesn't require much effort.
As I said, the H-scene on defeat is also a setting thing, it gets some people in the mood a bit like foreplay while it turns some off, admittedly more so with games that have in-battle cut-ins and such, but also just the thought itself. Going by how prevalent this model is, it's most likely a numbers thing, you're probably in the minority on that, some people also prefer having that agency taken from them or just not having to deal with the RPG stuff, but the target audience for that is probably smaller, supply and demand, all that. It's a relatively safe bet, it's worked well in the past, so a lot of developers probably also don't want to risk innovation, rather sticking to the tried and true method. It's a big time investment and developers at least want it to break even, even if taking risks could also dramatically increase sales.