Why do some IRC servers enable unregistered chat moreso than other chat services (e.g. Discord)?

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!