if commit messages are meaningful and the commits are well crafted (with the help of git add -p for example) this documentation can be generated from the metadata ;P Also, big end of day commits normally cover multiple different fixes. Which is, I hope you can understand, not very nice to have in one big commit.

If someone else decides your implementation of something is not good enough, and they manage to get enough buy-in to rewrite it from scratch, maybe they were right to start with?. And if your history is not clear about the why of your changes, you have 0 to defend your work

Also, rebasing is a lot easier when you have small commits, rather than a mega conflict.