Because I’m a healer… I have been through all of BfA. I have a healer spot in guild raids, people ask me to log in and heal their dungeon runs. It’s what I know and enjoy.
Our tank spots are filled by people who wanted to tank. I’d have to unseat one of them if I wanted to do it. I’d probably have to join a different guild entirely, and that’d require going through an application process where my only qualification is the BiS legendary
…plus I really don’t want the responsibility of tanking! It looks hard, let me be one of 4-5 healers please