there is some point to your argument but every discipline has a top championship, it allows others to admire whats possible, some to aspire to whats possible, and give everyone the chance to ride at their highest level possible.
To take your argument to the extreme no one should compete we should all play in our own back yards?
The fact that the sport at the top level, also any sport for that matter, does not relate/seem impossible to the ordinary competitor doesnt mean we shouldnt have a World trials championship does it?
A showcase is important surely. I have a scrapbook of my heroes Mick Andrews, mart, Bernie and the like, and the tricks and things they did. Alot of older riders will remember mick andrews going over a VW Beetle sideways, did we all go out the next week and I'll do that?
The fact that the FIM have pulled the rug from the 125 championship and systematically slowly ruined the WTc seems to be as much of a problem as ever.