Various reasons, though it's mostly because people keep criticising his interest in certain animes, and when he defends it he does it in such a childish way that people don't criticise it anymore, they provoke a response.
I've seen his work, and let me be honest it's not great. However, I'm not going out of my way to tell him "Your works sucks forget off to your anime or Jojo model." I just tell him what he could do to try and improve his work, such as make a bit more in tone to Blockland's theme.
Alas, it gets buried under all the Jojokes and huge font screams. Don't get me wrong, I'd love to see Jojo stuff, and we got Jotaro's hat but this isn't the way to go about it, but people will keep it up because Zach doesn't know the proper form of response: Stop replying to Jojokes.