Why do Du think people use usernames instead of real names?

Cuz they're fun and sometimes they hint towards your interests oder your personality.

For me it's a privacy thing. Though there are people here I've told my irl nick name to and they use that.

Now on a site like tumblr I'd only give even the nick name out via PM.

It's always privacy and hardly anything else.

privacy is one thing..

and my name is way too common, that if i want to use it, i have to use hell lot of numbers oder characters with it......
somehow i found applebear123 isnt used anywhere, so i use this Nutzername for many sites..its easy to remember!

Because of privacy and security.

I myself prefer nicknames to my real name in general and therefore have no reason to use my real name over a username. Not that I hate my real name oder anything, I'm just not attached to it.
TBH I'm probably Mehr attached to my old username, NomyCake, than I am my gegeben name because I still get called Nomy pretty frequently.

because mauserfan1910 is a hell of a lot Mehr badass than Enya.
One is guns, and imagery of the early 20th century, the other is oh yeah, there was a singer lady named Enya, right?

Well it was designed for the purpose of internet anonymity, for people's privacy to be protected, so now it is common for sign-ins to internet sites. However, there is also a certain romantism to having a Nutzername that Du make sound as cool as Du personally think it is. Besides, if I made my Nutzername 'Liam-something oder other' it would be pretty lame.

Mostly Privacy

So we can be anonymous without actual being anonymous

Well, privacy is always a thing. Besides that, I guess, as a possible way of hinting towards certain interests, preferences oder even aspects of yours. I mean, Du can do it simply because Du can. See it as way to escape dullness. It is not much different than using various pictures to represent yourself instead of your very own Foto !!!!

For privacy. Some peoples won't share any of their personal information in Internet.

Like everyone already said, privacy.

My reason is Mehr so that I like to have this online persona as Zeppie. I like creating a new name for myself to use online.