Why do tourists all want to 'avoid the touristy areas?'

I live in a city with a LOT of tourism (Edinburgh). Every day there are posts of the city Reddit page (and Facebook and Insta) all saying 'I'm coming to visit your city for the first time but I want to avoid the touristy areas, what are some hidden gems?' These are literally tourists who don't seem to think they are tourists. Don't they realise that if the locals told every tourist about the 'hidden gems' - then they'd just be yet another place full of tourists?