Music is a ever-changing landscape and the two artists show that. Both are well-known musical personalities, I don't think you can blame this one on the music industry as both artists record records for independant labels. The Music Industry produces shite like Mika, current no.1 in the UK etc., neither of these bands are built by a machine the industry has created (Take That cough cough have so this). Bjork is currently recording her 10th album and has always maintained a decent fanbase. She even hit popularity in the UK during the 90s.
You have to realise Glastonbury's aim at its fanbase and these two acts do that.