Things Mozilla have done a few times.[0] All with valid reason. 30 years without a rewrite is pretty rare for any piece of software. 0: https://en.wikipedia.

Things Mozilla have done a few times.[0] All with valid reason. 30 years without a rewrite is pretty rare for any piece of software. 0: https://en.wikipedia.org/wiki/Netscape_Navigator https://en.wikipedia.org/wiki/Netscape_Navigator