This explains why they sent me a “we miss you” email the other day. Thanks for sharing, I’ve deleted my account since I don’t use it anymore.

Think of it as an advertisement or a road sign. You want your message to reach as many people as possible.

Normies don’t usually find their way to Linux on their own. Hell, most don’t even know a third and fourth option (BSD) exists. By being on as many platforms as possible, more will find their way.

For what it’s worth, GitHub is NOT the place where kernel development takes place, that is just a mirror. Have a look here to see where development happens.