R/L does fluctuate in terms of "hipster", but considering last year included The Cure, Crystal Castles, Band Of Skulls, The Vaccines, Florence & The Machine, Black Keys, Pulled Apart By Horses, etc. across the main stages it's pretty obvious it's not a lne-up that LP would fit into.
they may be good to watch live (slightly biased as we're on LPL ) but that's not the only thing a festival promoter has to think about when approaching and booking bands to play. if you have too mixed a line-up that tries to appeal to too many people, the festival isn't as big a draw since you'd only being going for a few bands here and there, not for the full line-up - R/L would do a UK Sonisphere '12 on us if it tried to be way too diverse.
LP's too associated to Nu-Metal for the audience R/L's promoters were trying to attract last year. who knows, they may be on a line-up in future, but it'd be a big ask I think.