SirPrimalform: I think you're making a big assumption here. Are you sure GOG are refusing them because they're visual novels?
IMO you're making the same mistake as the people who assumed Hatred was refused because of its content. We don't know why GOG refuses things, perhaps sometimes it's simply that they don't think it's a good game?
Kerchatin: Well,
according to the developer of HuniePop they do supposedly have this policy:
"Before we released HP I reached out to GOG but unfortunately we were turned down because they have (or had) a general policy against carrying visual novels, which is totally understandable. I tried explaining that HP isn’t a visual novel but I never got a response back. No big."
Okay this is pretty silly, granted GOG has been known to do silly things like initially rejecting Xenonauts for being too high priced for a indie, seems at the time they felt Indies shouldn't be more then 14.99.
I don't get the logic behind this outside either it being the stigma of Visual novels and some of the people they attract. I mean if I had a dollar for every prev that gets all bothered that they can't see nipples or pornographic scenes in some of the visual novels on Steam like the Sakura games or NEKOPARA Vol. 1 I would be better off financially then I am now, not insanely wealthy but I could easily live off that extra income and be able to reduce how many hours I put in at my job.
But still if that is the case, it's still a poor excuse to not allow visual novels in general but I can't see that being the case since we have Hatoful Boyfriend and Long Live the Queen here, it's seem more possible to me that those games just didn't sell well enough here.
Even so it's still silly to go well we have two of those types of games here and they didn't sell well enough so thus we don't have enough of a market for these types of games since you can't really base if you should carry a entire genre of games based on two titles.