I suppose for simple libraries this might be possible (e.g. left-pad) but how would you know in general that something is bug-free? `units` was introduced in 1979 and is still one of the canonical examples used in automated program repair research to show that new bugs can be found even in extremely well-studied codebases.

I think people might be:

1. Implicitly assuming that all nontrivial code has bugs, and 2. Using recent commits as a signal that means, "If I ran into a bug, there is someone who might fix it (or at least accept a fix PR) to take away my immediate pain.