And why should a cleanroom implementation be an infringement? It is not a true derivative copy. Either way, software is more akin to language or math, certainly not mechanics. We have copyrights for language, and narrow patents on applications of mathematical formulas (which in itself is debatable in its justification).

Copyrights are sufficient. You shouldn't be able to tell someone they can't use a certain software algorithm in their own program, in a different language, in a different domain. That stifles innovation.