[t43562]

Rewriting something you wrote yourself makes sense. i.e. who knows better than you what the bash script does and why? You did it with bash - probably quite quickly but now you understand what's needed you can do it better the second time in a language which might be a bit less flexible but is much faster.

As for writing code to be replaced - well I can understand doing it but generally I've been in companies where you never get a chance to go back to anything that doesn't seem to be critical to the next requirement from the business - and they always have more than you can do.

The big rewrites are almost a response to this - no improvement can be justified unless it enables so many new features that the business decides to sign off. But because it's such a big change it is also much much more risky.