I can't speak for every case. At my work, we've done some rewrites. On the back end, we've seen 20-100x improvements in performance and the code is easier to ma

I can't speak for every case. At my work, we've done some rewrites. On the back end, we've seen 20-100x improvements in performance and the code is easier to maintain after switching many projects from Perl to Go. On the front end, we had to switch because the framework was no longer getting security updates (simple js and html from a symfony back end to an API driven SPA). I can't talk to the benefits of the front end rewrite aside from allowing us to dog food our APIs and allowing the front end teams to use tooling of their choice.