The patrons of a restaurant contribute their appearance. A fancy restaurant is going to want to exclude people that aren't fancy, because that would be contributing "garbage" to the atmosphere.
If you were a librarian, would you only make the top 100 novels available? Why circulate books that aren't the best?
Your second argument in favor of Geocities is that future brilliant web designers may use it? Ok they might, but if Geocities didn't exist they'd use something else. And I'd argue they'd learn faster and better habits by learning with some other tool.