If I'm travelling I pick a festival with enough that I want to go to that I get value from my season ticket, since I'm paying for accomodation anyway.
If there is a local festival I might go to the fringe even if booked acts don't thrill me.

There are 2 kinds of fringe, too. The programmed, free, events, and the spontaneous unofficial (for those who know).

There should be room for all, and when I have a season ticket I still enjoy a mix of concerts and sessions.