Catch, I understand your point. So, let's organize races with limited resources. What's wrong with that? It's more accessible and closer to the people. Where did you get the 90% figure from? Or maybe it's based on social surveys? ;)
90% is based on experience. A typical player will choose the path of least resistance. If it takes them half an hour to install an add-on and two hours to roughly learn it just to play in a tournament, they will prefer to spend a minute going to another tournament page on a different resource where they won't have to do any of that.
The seriousness of a tournament is not determined by the location, but by the organization. It's strange to hear such questions, honestly. Since the premise is incorrect, it's pointless to answer further.