I have a Microsoft account for OneDrive, and if that account ever gets banned — say, a defective algorithm thinks I've uploaded pirated content when I haven't — I don't want to also lose access to a game I've already paid for. Right now, the accounts are separate.
It reminds me of people who lost access to their e-mails and photos for making YouTube comments (a completely unrelated service).
So far this is the most convincing argument to me. This is why unified accounts are problematic. If you get banned in one place, you get banned in all completely unrelated places too.
1.) Not wanting them to link another of my email addresses to them
2.) I don't want or need a Microsoft account just to play Minecraft
But the mojang account was fine? That's my point, they already have your email address.
A lot of us(longtime motivated Minecraft players) bought our first accounts when we where fairly young, and often used emails from parents/school, which we no longer have access to. Another reason why this is a huge deal is that this means Microsoft terms of service apply. Also this means that the random account banning that can be experienced with Microsoft accounts will come to Minecraft.
Not only that. I had used a normal email address and still had to contact support multiple times for that account transition a while ago. (Or where there even two?)