Of course that's just another reason some people don't like to GM. They don't want that distance.
Precisely. Or, at least, I don't want that distance from my PCs.
For several years, I was pretty much GM-only, running my (ongoing) Dungeon World game. I was kindly offered a short-run 4e game by MichaelSomething, and around the same time cordially invited to Hussar's group, which I'm still part of now. None of my attachment to my PCs has eroded from the several years spent being GM. I simply don't attach myself to NPCs the way I do PCs. It's...just a fundamentally different experience. Heck, I try not to even attach myself to the
world as much as I do a PC, because becoming precious about a world means denying players the ability to truly shape it and drive it toward new things.
I guess the only GM-side thing comparable to how I invest in player-side PCs is...the
campaign. Not the setting (though I care a lot about keeping a setting consistent!), not the NPCs (though I try to portray good ones, whether allies or foes!), not the magic systems or the plots. It's more...the entirety of the campaign. If that campaign truly comes to an end, I want it to be a good one, whether a pleasant "and the adventure continues" state, a "and so they rode off into the sunset" sort of thing (which may be anywhere between purely sweet and very bittersweet), a "heroic last stand that made a difference", or some other reasonably satisfying, non-downer ending.
And that's...pretty comparable to my stance toward PCs--my own and others. I get invested in
other PCs too as a player! I don't necessarily need to see them get Happily Ever After, nor even Happily For Now. But I do want their story to reach
some kind of satisfying conclusion. Tragedy can be satisfying in the right context, but the right context is hard to build in a TTRPG environment. Earned victory is of course the most satisfying, but even just "earned reprieve" or "freed from burdens" etc. can be enough.