You see the photos after the festival. What you don't see is the photographer spending hours moving around before, during and after the performances, they have to anticipate moments rather than simply react to them.
Where will the artist move?
When will the lights change?
When will the crowd react?
They may also be working under restrictions about where they can stand and how long they can photograph an artist, and they don't get unlimited chances.
A moment happens once.
If the photographer misses it, it's gone.
That perfect festival photo can sometimes come from a split-second decision.