Probably to make the whole process speedier and cheaper for the airline. You'd have to completely finish boarding for lower classes and then give a decent grac

Probably to make the whole process speedier and cheaper for the airline. You'd have to completely finish boarding for lower classes and then give a decent grace period for first class passengers to just show up at their leisure. Also first class (and often business) are kinda separated so no one stares you down. I fly premium economy sometimes and you're the first to board and sit upfront and then you have to watch everybody walking by! It's a world of difference between premium economy and business, sigh. Norwegian Air Shuttle had a pretty cool idea with their premium cabin. It's not crazy expensive but the seats are so much better!