The issue with Anchorage is that even though it's in the USA, even at the airport, at least some (I don't know if all) of the "major" players are non-corporate locations (that's certainly the case with Avis), meaning they don't have to give miles/points/whatever, honor central reservation coupons and policies, etc. Usually you only find that halfway around the world (at least if you're sticking to airport locations) and usually you don't find it in the USA (at airport locations).