[hocuspocus]

I think it's a little more complex than that:

* Some low-cost airlines (like EasyJet) are pretty much doing just that, their premium membership give you access to priority lanes without any other significant benefit (since they don't really offer any).

* I don't think anyone wants ticketing to get even more complicated. It's obviously a lot easier and more rewarding for airlines to treat their frequent/business flyers well and make everyone else take the slow lines.

* First and business classes don't fill up the planes, airlines are directly impacted by shitty airports that can't embark/disembark/transfer 80% of their passengers (and luggage) quickly enough. You can't say there's zero incentive to fix the problem.