It's not so much that people didn't set up a Microsoft account, it's that they couldn't. It required verifying the email you originally used to buy the game, which Mojang had never required before, and you had no way to change the email. Lots of accounts were tied to 10 year old emails that had since been shut down. The only other support path was to give them the credit card transaction ID or something, not feasible if you got it as a gift.