Don’t rely on it. One the greatest and most enduring myths regularly talked about on here is that Glastonbury attendance is affected by the line up.
Although I do agree that both The 1975 and Sam Fender as shockingly bad choices for headliners
Just when I thought it couldn't be any worse... Going from a weak headliner to a completely irrelevant one.
Given how fast the music industry is moving, and if these turn out to be the actual headliners, GF will lose much of its relevance. On the bright side, getting tickets will become easier once again.