https://xkcd.com/1205/ is relevant here.

Our codebase is somewhere between 200k and 300k LOC. Running the flake8 suite takes minutes. We haven't integrated ruff, but during a test run it ran in less than a second, IIRC.

So, with, say 20-30 commits per day, that's about an hour, every day. Sure, it's not like we're usually sitting there twiddling our thumbs during builds, but sometimes we actually do have to wait for a build to get ready. Just the waiting time during those rare occasions add up.

[edit]: flake8, remarkably, dropped roughly an order of magnitude in performance between version 2 and 3. So that didn't help.