I'm pretty sure cybernetics died out because it had a mechanical feel and didn't fit well with the simulation-based philosophy of the universal computer. But simulations need to be simulations of something, so why not feedback loops?
(3) Tue Jan 09 2007 21:13 What happened to cybernetics?:
Cybernetics was pretty big in the 40s and 50s. People had all sorts of grandiose goals for it: using it to understand living and social systems, for instance. But it kind of died out; it's the one thing in Stanislaw Lem's fiction that seems dated.