This was a longstanding fediverse complaint, which was quite remarkable to me. It was described as a "missing" feature even though you never had this ability anywhere else let alone the fediverse.
If you get a new email address, it doesn't bring your contacts or your history of emails with you. If you make a new twitter account, same thing. And of course, don't even think about trying to port, say, your facebook stuff into a youtube account. But if the fediverse can't, then it's a dealbreaker.
If you truly want to channel the limitless depths of human creativity, give a Comment Section Skeptic (TM) every fediverse feature they say they want. Then wait and watch as that creativity goes into action, as [insert new feature] is now the new dealbreaker. It is and always will be an endless game of whack a mole.