It's interesting that you note it only takes one person to undo the progress -- by the reverse token, every person who works in this way adds value to the practice and the history, which is why (and how) I've advocated for and to individuals to spend time on it.
Any one person can muddy the history up (by ruining bisect, say), but any one person can also improve it (by leaving good notes and right-sized commits whenever possible).
I notice that I get sloppy when I'm working on a repo with others that are sloppy as well. I guess the reason is that, if looking at the Git history is not useful half the time (because you end up at uninformative commits by other contributors), then you stop looking at the history, and then there's not much reason to leave it in a super-clean state anymore...
Any one person can muddy the history up (by ruining bisect, say), but any one person can also improve it (by leaving good notes and right-sized commits whenever possible).