I guess if you earn your income from tourism, then the more the merrier, but I can understand if you live somewhere like that and not be invovled in that industry it would be a pia.
As an example, we are in Monchau a small town in Germany close to Belgium, during the day there were lots of tourists but most had disappeared by 5pm.
Same with places like Cesky Krumlov, it's best to try to stay overnight and not do a day trip, imo.
Now off to Spa and a quick lap of the Nurburgring tomorrow, before heading down to Trier for Rallye Deutscland. Guess I'm contributing to the issue as well.