For celebrities maybe. For instance for nongeneric usernames on Instagram there are "claiming services" that involve some combination of paid off customer support and Media Partner Panel's that allow them to steal usernames. There's also the classics: SIM swapping/email compromise followed by password resets, extortion, etc. See how @N had his username taken and only got it back a month later after complaining publicly. People have also observed people who work at social media companies taking desirable usernames for themselves.
Reddit does this now too. IIRC there was much anger around the deposing of user u/instagram
It's also the case that Discord users can change their username and display name at any time. It isn't clear to me if this functionality will change in the near future. How much "tech debt" is it really, and why?