Well, I hardly think evolutionary theory is the model of consistency we should all aspire to.
In the engineering side of my company, we can re-use design components where appropriate and that is certainly most efficient where it is applicable. There are other situations where we have to start nearly from scratch, because the solution demands a different design from the ones that we already have stored in our AutoCAD templates file.
It's design to fit the specified operating parameters. We do it all the time.
At random, with no rhyme or reason. Just as predicted by ID.