It's more about should rather than can. Fair enough if you're a committed fan and want to go see their tour show, but as a festival headliner they seem too esoteric/downbeat for me. Hardly the sort of thing you spend a day building towards and then gonna career off into the night with..
Surprisingly the best headliner I've seen at EOTR (this will be only my fifth year..) was Vampire Weekend, but that was a slight one off as their album release date had been pushed back loads so they just played loads of old songs which as a young-ish millennial hit all the right buttons..!