Spotify released some numbers their data revealed.
It shows that there is a significant bump in streams for bands that are performing at festivals than for comparable bands that are not playing festivals – by as much as 14%
Anecdotally this makes complete sense.
The audience generally finds it more fun to know the music when they go to a concert. For festivals of course people won't know all the bands, it makes sense they'd want to do some pre-festival listening.
It's nice that the data shows that the audience is doing their homework – to have more fun at the festival.