Because that's not how activity works. By the very definition activity is based upon how active you have been on the forum and you haven't been very active at all. On the contrary, I would argue it wouldn't be fair to everyone else who has built up their account and rank over time by putting in the work and effort for others just to be able to create an account, abandon it for x amount of years then come back and magically be a Hero or Legendary member etc. This would just encourage even more lazy account farming if it was possible to achieve such ranks merely over time.
Also, have you actually been here since 2012 or did you just buy a hacked account to try appear like you have some history here? There's a huge gap in your post history from May 29, 2014 to May 2016 and then May 24, 2016 to April 2017 which is usually indicative of a very likely hacked account. This is why activity is actually a good system because you may or may not actually be an old member but you certainly haven't been an active one or earned the ranks you would have achieved naturally had you been actively posting.
I got my nickname since 2006, and I got my whole digital life under this nicknname.
