It occurs to me that part of the reason most people react to cockroaches as if confronting a anthropomorphic turd is that, in terms of evolution, our hysteric human reactions convince the cockroach that it needn't develop the ability to bite. Everybody wins.
(Listen, asshole, I know that on rare occasions, cockroaches bite humans. But it's largely harmless. What I'm saying here is if we were to not freak out when a giant golf ball-sized insect shoots across the bathroom floor like the light cycles in Tron, the cockroach may, as a species, decide it is no longer getting things done and needs to develop flesh-melting super venom. Bitch.)