Readability belongs to documentation. Code should have certain technical aesthetic, it should be easy to navigate it, but why its operation should be obvious more than that of any complex mechanism? Nobody demands a mechanical watch to be readable or have meaningful names for the parts.

It is not just performance. A minimal component gives you flexibility: you may make the whole system performant or you may trade extra performance to reach a different goal, such as robustness or composability. It is a more fundamental principle, common to construction in general: a thing should do all it has to do and should not do anything more.

Optimisation usually sacrifices some flexibility and/or robustness.

Valid if needed, but exists