At least there is a demo and at least demo racers have full rights to post on the forum... iRacing for example doesn't even have a demo mode, and you're only allowed access to the forums if you're a subscriber! It could be worse...
Because the devs chose it to be that way. It's their decision... you could keep giving more to demo users, but there will always be complaints about something that isn't offered in the demo that 'should' be offered... Where does it end?
Exactly. Besides, getting avatars and things are pretty common when it comes to games and their forums. Demo or unlicenced users cannot have avatars, where as the non-demo users can. Just how it works. Like it or lump it!
Actually, it's because in the past, some demo users abused it with inappropriate avatars, thus all demo users got access removed to upload them, some older demo users still have aavatars.