When I joined the internet, there was Usenet. And Usenet etiquette (at least for de.* which is what I had to restrain myself to due to the general lack of English) required you to provide a real name, so that's what I've done.
This made me much less reluctant to use my real name later on.
However, just as my real name, my pseudonym also stuck and I try to get it whenever I sign up for a service. That way I'm twitter.com/pilif, github.com/pilif, even facebook.com/pilif, though I don't use that.
Unfortunately, on G+, I can't be /pilif. I have to be pilif123459 or whatever. Too bad.
I think the trend until mid 90s was to use your real name. Then it kind of changed at some point in 90s to nicknames. Now we seem to be going back to the early 90s when it was common to use your name.
German Usenet was and still is (in)famous for demanding real names.
In the late nineties and early 00s there ware huge wars between those who campaigned for pseudonyms (usually labelled "net terrorists", although honestly most of them really were trolls) and those who insisted on real names (labelled as "Blockwart": https://en.wikipedia.org/wiki/Blockleiter).
Of course it's immaterial now. Most of the "net terrorists" left, many of the "blockwarts" mellowed, and in the end Usenet is dead and both sides tolerate much more than they used to, just happy to see a few more postings.
This made me much less reluctant to use my real name later on.
However, just as my real name, my pseudonym also stuck and I try to get it whenever I sign up for a service. That way I'm twitter.com/pilif, github.com/pilif, even facebook.com/pilif, though I don't use that.
Unfortunately, on G+, I can't be /pilif. I have to be pilif123459 or whatever. Too bad.