For small projects, rewriting is often superb. It allows us to reorganize a mess, apply new knowledge, add neat features and doodads, etc.

This. I'm coding to contribute to a open-source software with very small amount of coders, and with a non-mainstream Domain-Specific Language. A lot of the code I did before has been proven to work from times to time, but they all could benefit from better outputs and better GUI. So, I end up reengineering the entire and that'll take a really long time, however, I do a lot of tests to ensure it works.