I agree with almost everything the people said here, but I'll be honest, I didn't read everything.
So I'll add my 2cents:
-A lot of people want data D when they play AVG, that's unfortunately why male presence or futa are more popular than lesbian only games
-There needs to be a distinction between Yuri and lesbian games. Yuri is a subculture all by itself, it focuses more on the romance and subtext than homosexuality itself. I love Yuri, and I'm glad to see that through recent years it's been getting more and more popular.
-Some lesbian games now, focus way too much on homosexuality itself and are openly LGBT(and whatever comes next), feeling more like propaganda or a piece of candy for a limited audience. I personally despise most of those games.
-And finally, there are the lesbian games with no real political agenda behind them, that just want to tell stories with lesbian characters. i like those games too.
But most people aren't interested in any of those games. As I said, a lot of people want to see a dick somewhere, after all, it's not sex if there is no penetration, right?
About the popularity of lesbian porn and its correlation to video games. There is none.
People who watch porn want a quick nut. Seriously, who watches a cut 10min video for the scenario?
Video games require more involvement from the player and the developer.
A level of involvement people who simply watch porn aren't necessarily willing to make (first, it's a video game, and people kill because of video games, and people who play video games are just lazy and parasites of society, and second, you need to... you know, that thing you do with those things full of paper old people have in old furniture, yeah you need to READ, and only nerds do that.)
Finally, someone said homosexuals are by default a minority of every society (or something like that), well, welcome to let's learn to make the difference between fiction and reality.
Let's go back to porn, some women like gay porn. A lot of straight men like lesbian porn. And even without talking about porn, homosexual romance is attractive to the other gender too even if their readers are straight.
Stories are not the reality, that's why people like stories, it permits them to see things from another perspective without having to review their own style of life. (that's also why I hate media with a clear political agenda behind them, I'm looking at you Netflix and other LGBT-backed media)
But to answer the original question, I'd say it's both.