> There's no technical reason, other than thinness, for the way Dell soldered the RAM down, for instance.

That's a sentiment that's been repeated a lot, and it's not fully true.

One important property that soldered-on RAM has is increased security. There's been a demonstrably practical way to break full-disk encryption with physical access to a turned on or sleeping computer by re-attaching the memory quickly to another computer. The keys then can be read from the memory.

That's not a vector you have anymore if the memory is not removable.