I experienced another aspect of this when I once drove 35 miles to visit a nature reserve, only to find that its car park was being used for the start and finish of a charity walk. There was no room for me at all, it was chock solid with cars and vans, as too was every pull-in along the access road, and I had no choice but to think of somewhere different to go.
EDIT: Just remembered another example, there was a 24-hour triathlon taking place when I walked my circuit around Snowdon last September, I think it was for charity. I passed Llyn Gwynant camp site which they had completely taken over, there must have been over a hundred tents, not to mention marquees, vans, lorries and a public address system. Imagine if I had arrived late, planning to spend a peaceful night there! Southwards beyond there, the path was a quagmire, churned up by goodness knows how many runners having used it earlier.