I'm not saying that I prefer the soldered-in versions, but back when I had a Mac with user-replaceable memory, the RAM would get unseated from time to time as my machine got jostled around in my bag and I'd have to open it up to fix it. I imagine that the Genius Bar saw a non-zero number of people bringing in computers that wouldn't boot because of this. Also, soldered-in saves space and thus helps with their pathological need to make MBPs thinner.

It's hostile to users who want to upgrade RAM, but pretty friendly to everyone else. It gets into the point of this article...when Apple looks at both demographics, the group that doesn't upgrade is much larger. Apple used to make decisions that would cater to the more non-mainstream use cases of their pro users. Now, they're focused almost entirely on the mainstream users.