Ideas generally need paid votes.
It depends on idea. But if you need your idea win and created fast - the simplest way - buy votes.
Why you say that? Lack of content of those themes or little support with votes on polls with those themes?
Lack of content of those themes
I know some nations are very anti-incest and their laws are quite difficult even in the hentai scene. But generally its just taste.
Ye, just gotta like what cha like lol
but could be more
Dad / Daughter pairing
If you'd like to see dad/daughter pairing and no one wants to vote for you, buy your own votes. If you can't do that, then there's nothing else you can do