Probably because amiga is a 16 bit system and the interest in old arcade games wasn't too strong at the time. People prefered playing crappy Tiertex ports I suppose. BTW new version is out, possibly slightly faster.
Yes, the v1.1 is a bit faster on A500 machines. Good work. While you don't quite get fullspeed, like you would on an A1200, the game is at least playable on 7MHz Amigas.
