Actually, going to have to completely agree with Lord Zero here and I think you're highly misinterpreting what he meant Joy.
A video game is simply electronic software that revolves around human interaction with a user interface to generate visual feedback on a video device... it's never been defined as any more then that. We call RTSs "Real Time Strategys" because they're strategy games played in real time. We call games "First Person Shooters" because they're in the first-person perspective and involve shooting. We call "visual novels" because they're games based off their visuals and they read like a novel... and they're still marketed as games because they fit the original definition for most people and especially businesses. If it doesn't count as a game for others, it honestly feels about as silly as saying social games on cellphones aren't games because that's not how it's traditionally done, which plenty of people do but we keep calling them games anyways. We don't call JRPGs Rorupureingugemu (or whatever the proper romaji is) because that would be correct if we lived in Japan, that would make no sense in an English speaking country. We can describe a role-playing game a million different ways, a war game, a murder game, an MMO, virtual chess, whatever we wanted to call it, but just describing the thing would make it pretty clear pretty fast rather then giving it a billion subgenres.
I don't think he was trying to be offensive, because even I'm mystified by what the question of this thread is... because I literally don't quite understand what we're asking here. I really do get the difference in meaning with the different names, but it's pretty apparent that "galge" or "eroge" is not a widely accepted name for anyone but the niche fanbase. Old Hirameki games plastered the boxes with the term visual novel because it was the most neutral, descriptive, universally understandable term and a lot of other companies just rolled with it. It's an easy to understand, culturally acceptable, marketable term. Eroge is not always accurate and is not a very marketable term, Galge, Bishojo game or even "pretty girl game" would not be culturally understandable at all and very unmarketable. It just happened to fall that way that visual novel works, just like RTS is more marketable then "war game". It's all relative though, a name is just a name. The recent trend is to call a lot of recent shooting games like Halo, Gears of War and Dead Space "space marine shooters"... there's no "rules" in naming things. Like... this I really don't mean to offend at all to state, but the second line of your signature (hater of weeaboos) seems ironic when we're questioning why we don't use the Japanese term that virtually no one outside of VN culture would understand instead of a universally understood and accepted term.