I don't think the market is small. I really don't know why more devs are not making ntr games. I think one reason might be due to censorship and strict patreon rules which deter devs from making games with darker themes.Man i wish we would get more western styled ntr games soon with animations and stuff, sadly all the devs are making most dogshit vanilla games with few exceptions like forget ntr not even corruption or darker themed stuff is being made bruh. Is the market for ntr games that small or something? Like i know there are more vanilla players but still there should be more ntr/nts games considering we are the second biggest group here (not to mention half of ntr players are women if the words a certain mod on discord is to be believed).
Another reason might be that it's a bit harder to write a compelling ntr story. NTS stories, the not so good ones at least, are simpler to write and don't need to be so dark.
I personally hate the drought which is going on and literally no one is making a good use of this genre. There are/were a few Japanese devs like the Black Rune game but they keep disappearing.