Because every minute the dev spends developing ntr content is not spent creating other content.Evangelion to be fair if you shut off the "NTR" content you'd never even know it's in the game . so are you bitching to bitch or are you just trying to be cool?
You want to create an ntr game? Fine, do it say it is unavoidable and go on your merry way.
Either have ntr or not, but having both makes no one happy.