I use a pseudonym.
As to why I use one on Tapastic, it's because it's on the interwebs, and most of my internet presence is under the name MxxPwr. So, I felt it would be easier to direct people who know me on the web to this site, if my pen-name and internet name were the same.
As to why I use a pseudonym on the web? My history with the web, I guess. Almost no one used their real name in the 90s. Doing so protected you. Not just if you were a troll, but also protected you from trolls.
I realize expectations are different from people on the web now, and if I were to ever have a Patreon, 'business' Twitter, YouTube channel or the like; I would probably be more forthcoming with my name. But, until then...
Not that it's out of fear, fear. I mean, my real name is Frank, for what it's worth. Just my cautionary experience with the web.