Stack Exchange allows its users to change their display name once every 30 days. This was a little surprising for me; on most previous sites where I was an active member, you picked a (permanent) username during registration. It often (but not always) needed to be unique (though that might be because you also used it to login). But once you chose a name, you were basically stuck with it; to change it, you'd need to sign up again (and thus losing your account history) or write a very compelling story to the site administrators with a request to change your name. On those sites, you'd still had plenty of personalization options in your avatar and/or signatures under your posts.
I can imagine valid use cases for wanting to change your display name; if you signed up as a teenager with a name like UnicornLover1234, and you want to change it to something more professional since that better suites the current phase of your life. Another example would be a gender change; that's something people change their real name for, but it's not done lightly and takes a lot of paperwork.
The main drawback of the current system on Stack Exchange is that, at least for me, it's sometimes hard to keep track of users, especially since they can have different names across the different sites in the network (but that is not the main point of this question, since it only applies to Stack Exchange). Sometimes you see a user where their reputation and/or the way the write indicate that they are long-time users and your paths might have crossed before, but it frustrates me a bit that I don't recognize them. Just like you meet someone in real life who you fail to recognize from previous encounters; that always embarrasses me.
Of course, if a user temporarily changes their name to match the current 'season' (e.g. Halloween), but does it in a way that they're still recognizable as their former self, that doesn't cause any confusion.
It could perhaps be argued that Stack Exchange wants it users to focus on content, not on the users who are posting them. But this is simply not how the human mind/a community works, not when focused on objective Q&A like the technology Stack Exchange sites, but especially not when it comes to discussions on Meta.
Therefore, I was wondering: are there any objective benefits of allowing users to change their display names? The answer may apply to a specific kind of online community (e.g. one where anonymity is very important), that's fine.
Note: I'm not asking Stack Exchange to change their policy; I'd ask such a question on Meta Stack Exchange but I guess I've learned to live with the current system.