Because I see a vast difference between the following two things.
"Alright guys. I'm running a campaign inspired by Archaic Greece mixed with the Trojan War, the Greek city-states vs Persia but with lots of myth stuff. Lots of races you can't play. No elves. And no, Charlie, you can't play dragonborn in my game. Why not? Because I said so, that's why. I don't like them, so you don't get to play them. If you don't like that, you don't need to play in this campaign."
"Alright guys. My starting campaign idea was Archaic Greece mixed with the Trojan War, the Greek city-states vs Persia but with lots of myth stuff. Gotta have options like satyrs and minotaurs, obviously. I'll be using a homebrew race for dryads, I don't think elves fit, but you'll get a lot of elf-y flavor out of that. I had a private chat with Charlie. He brought up some myths I hadn't heard of before, so dragonborn will be rare, but playable; I'd appreciate it if no more than one other player besides Charlie picked them, as their place in the world is...complicated."
The former is the always-cited "pulling rank", laying down the law, hard-as-nails, no-discussion, no-receptivity presentation always given in this sort of thing. The latter shows a GM who does, in fact, have a clear vision, but who expects to (a) need to persuade the players that that vision is worthwhile, even if they are the GM's friends, and (b) tweak and adjust and meet folks halfway, rather than tossing out an ultimatum that must either be entirely obeyed withotu question or entirely rejected (and thus the player rejects any form of participation at all).
Further, these examples already earn beaucoup sympathy from me, because they objectively cannot be just carbon-copying the now-trite tropes that have reigned supreme for fifty bloody years over this hobby. By being an intentional step away, they are necessarily, from the ground up, built out of examining things and questioning what fits and what doesn't. I inherently expect someone electing to do this to have actual, thought-out reasons for what they're doing, as opposed to tradition exclusively because it's traditional, screw you for having tastes that weren't written about by an author 70 years ago.