What's the cause of that as wasn't Futanari stuff formed so people can have their girl on girl action and dickings at once? Was the separation caused by the rise of yuri fans who consider dicks to be the devil?
Because people searching for one often don't want to find the other, whilst people looking for both can either search for both or use ~. Separating them satisfies both requests, not doing so doesn't, so just like most danbooru tag practices, is as simple and pragmatic as that. Ideally, tags are always handled in this "what do people want to search for/find?" way, and the name is just a name, not our label of how we think things should be catagorized.
Edit: Also, biology thinks if you got balls and not ovaries, you're M not F, however society treats you. That's a pretty big difference in a sex scene.
Though I was asking about the divide in general as I've heard some yuri fans say "Futa isn't yuri!", though it might just be a sign of how the fandom split off and evolved. It doesn't help that Futa fans have basically taken over /d/.
But that's a good answer in relation to the board.
Serlo said: It's got nothing to do with fandoms, it's just a boring, pragmatic "what do people expect to find?" and/or "what makes the most sense?"
You are completely missing that "what do people expect to find?" is defined mainly by the fandom, i.e. people who are going to search and have more or less clear expectations about what they are going to find. Also see topic #2420.
I'm not disagreeing with neutral and pragmatic approach to tagging, in fact I support it. But in this case fandom did have an influence on our definitions. (I'm not trying to say that it's a bad thing, just stating the fact.)
Perhaps it is as simple a reason as "the usual definition of yuri does not encompass those with male genitals". (It's Shiroi Heya no Futari, not "Shiroi Heya no Futanari" :P )
jjj14 has it as I see it. Similarly, futanari does not count toward male or the 1boy//nboys tags. It's just "yuri = female bodies", "yaoi = male bodies". There do exist futa_with_male, futa_with_female, and futa_with_futa for more specific body pairings, and newhalf has been reinstated.