Hmm a few characteristics come to mind...
A company that knows that there are five times more requests--not consumers who have purchased, but mere requests--for iPhone cases than Evo cases. There are more consumers who have purchased the iPhone and will likely stumble upon Otterbox rather than already knowing about it and requesting it.
A company that has limited manufacturing and R&D resources.
A company that knows that Evos only account for roughly 1-2% of the entire Android market, and despite the good sales of the Evo, Verizon will probably sell more Android phones over the long haul.
A company that looks after its profits (but which company doesn't?).
I'm not defending their lack of cases for the Evo and the slow rate at which they bring one to market, but honestly, I can't blame them. We're phone-centric people, so of course we're a bit irked.