It works fine for members of my family and extended family that have Ubuntu installs on Intel GPUs. Light gaming and more importantly, hardware accelerated YouTube works just fine.

I'd be willing to bet that most people really only want windows to appear quickly, scrolling in web pages to work well, and to watch videos online.

Lots of casual gaming has moved to mobile, and never left the consoles. Hardcore gaming -- not most people.

That sounds like someone who has no idea what they are talking about. The open source drivers are a bit buggy. The binary drivers work just fine on Linux. Their performance in games is lower compared to Windows, but that is the case on OSX too.