I'm actually flying WN every now and then these days. Part of the reason is that I live very close to BUR, and my alliance of choice has a minimal presence on the west coast. When I go to the east coast and midwest, I care about the FF miles, the FF upgrade, etc. Due to flight times, I pretty much block out the whole day for travel, so I don't mind the longer jaunt to LAX.
However, for my shorter flights, it is ssoooo convenient to use BUR. SkyTeam has only a small presence there. I naturally gravitate towards WN, as they are a big player at BUR. It's great being at work (or home) within forty minutes of TOUCH DOWN.