There are two scenarios I want the cleanup to happen: 1) app is buggy and I'm trying to fix it by reinstalling from scratch, 2) I need to free disk space. Both are pretty rare, and in the second case I am already using a specialized utility like DaisyDisk to see where my space has gone.
> transient data files
/tmp? That gets actually auto cleaned up!
> settings
Maybe. Do we want macOS to introduce the concept of uninstall to shave a few of those kilobytes? Hoping programmers do not screw up with rm -rf /? I already hate it when I have to use an installer so that's a no from me.