Not that I'm complaining, I just find it kinda interesting given how so much stuff demands you sign up & register to do much of anything on a service or site.
Is it simply a cool cultural element that's persisted since IRC's been around? Also shoutout to all the old hat IRC folks out there maintaining their servers and enabling drop-in questions this way, much appreciated!
To wit, someone else could log in with your username and people probably couldn't tell the difference
There are service bots, that are used by many of the irc networks, that handle this within irc itself (nickserv, chanserv, etc…).