I didn't really ditch AA outright. I earned my AA miles way back in the 90's, including quite a few Alaska flights between SJC-SEA. Then had kids, changed jobs, was self employed for a while and my infrequent travel was on whatever was cheapest. When I started to travel more frequently again in 2012, it was still only like 6-8 trips a year and having experienced Virgin Atlantic a few times I decided to stick with Virgin America. Their relatively small network matched where I needed to go and heavy road warriors stuck with the larger airlines, so my silver status meant I usually scored upgrades (to their premium seats, not first class). When Alaska bought VX I became part of that program and I've been pretty happy with it.

You are correct that I do prioritize upgrades over million-miler status for now. But when I earned the AA miles (and before that 650K UA miles -- which was an intentional ditch) I was not aware of million miler programs and certainly not really thinking about lifetime status for retirement that was decades away. Now that a few of those decades have passed, it is something that I'm starting to pay attention to. I probably have another 10 years of heavy business travel and I expect I'll hit MM on Alaska. After that I expect I'll focus more on international travel rather than domestic. Not really sure if it would make sense to pursue MM on AA at some point, since 2MM seems to be their sweet spot and I'm very far away from that.