As noted above the premise of this thread is completely erroneous as far as US goes.

WN offers far better service (and I often get free drinks, not to mention pretzels and peanuts which UA has discountinued) than many legacy carriers on short flights. B6 also offers better legroom and no bumping. Legacies charge for crappy unhealthy snack boxes - that's of no use to me. Also easier to get an aisle seat on WN for last minute flights - almost impossible on legacy carriers.

F is the only class of service offered by legacy carries that is better than LCC coach product. And you pay for F - with miles, with $, or with status gained thru spending $ for many flights.