Why gc --auto is called so rarely?

Hello,

I tried to find places where git gc --auto is called, and found that there's only a few.

First, in *some* merges. That is, if there was a conflict during the merge, that is resolved, then it's not called.

Then in
* receive-pack
* fetch
* am

Is there any logic in such assignments? Why there?

In particular, gc --auto was called in commits earlier, but not in the recent versions of git.

--- Best Regards, Ilya Kantor