Gameplay.
Even the most well written VN just becomes a time sink. I can't spend time playing multiple at once without forgetting something crutical in another one. Beside that, I just get sick of reading text no matter how erotic the nsfw scenes are, since most contain far too much set up versus reward.
Half of this site's "games" don't even contain choices for the player to make. Worst offenders tend to be RPGs where every other step is a cutscene, with like mabye five battles springled inbetween. So yeah, gameplay is important, since why would I play another walking simulator or reading another VN. When I could get twice the reward minus all the effort from looking at hentai instead?
Games are meant to be played, not just watched or trudged through.