I think there's just more work and pitfalls involved in making NTR than say a vanilla harem game. You need good writing, good pacing in the story and the corruption, believable dialogue and setting...
There was this great story I read over on literotica recently called
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, before I spoil it I'd rate it an 8/10 and recommend it.
But here comes the spoiler,
What's that got to do with NTR games? Well if you don't maintain a good standard of writing/development/corruption all through your game, you could end up disappointing your customers and risking your good name and income, and hey nobody likes to have their hard work torn apart.
There's way less work and risk invoved im pumping out vanilla harem games, where the standards and expectations are far lower, and there's safer money to be made.