[myth2018]

Agree that you should never rewrite from scratch. However, I believe that almost 100% of rewrites are not actually from scratch: even if not a single line is reused, there will be plenty of experience serving as a foundation.

I'm not implying that's always the case. Besides, in some cases, past experience is deliberately not taken into account -- I'm aware of a handful of systems written in procedural languages which performed not that great and were replaced by naive object-oriented implementations. Went really bad.