UA loyalist prisoner here. For domestic flights, they are the only airline operating SEA-WAS redeyes. I suppose if I really wanted to save $50 then I could add an early morning connection somewhere, but for now, I'm happy to pay the slight premium.
For international itineraries, it's hard to beat the *A network (though hard product can be a bit lacking). I don't think SkyPesos get me very far in Asia, and it seems in Europe, I'm constantly reading about AF strikes.
If AS added a redeye, I'd consider changing over ...