Some one hit on the real problem, which was power. The Amiga just didn't have enough for far to long. The 68000 cpu was a great chip, but just wasn't powerful enough.
That why Word Perfect quite development on the Amiga. Their V5 needed way more power than the 68K could offer. WP needed at least a 68030 to run. While there there were accelerators with this chip, there was no Amiga model with it. The Amiga 3000 was just to late in coming.
While there may have been other reasons, this was surely the main one.
