What exactly are you getting on legacy carriers?
Better service? I don't think so? More legroom? The data on this says otherwise. Meals? Do you really need to eat goyslop every 3 hours? CC rewards? There's rewards for LCCs. Fewer nogs? I don't think there's a difference, that's mainly regional.
Southwest offers the best value in domestic US air transport and its not even close. I see no meals as an upside, less chance of dealing with someone with poor table manners and NO RJs. That's got to be the biggest advantage. I don't have to ride an CRJ ever.