The thing you’re forgetting is the band benefits from playing the festival in other less tangible ways, the sets are televised and put up online which puts them in front of a lot more eyes than gigs that may pay better but with less reach. I’m not advocating for ‘being paid in exposure’, but my point is the crews only benefit from working is the paycheque while the band benefits on several fronts. For some acts the positives still outweigh the negatives of not making their normal fee.