If I'm taking a project in a completely different direction, with different people, I might not care about commit history very much. But I worry more from a licensing standpoint. Unless a project has a strict copyright re-assignment policy (uncommon) where all contributors sign over their copyright (not just contribute their "patch" under the designated license), the copyrYight history is lost or at best muddled.

Now, in practical terms, one can always go back to the original repo and find it. But if I was doing this in a corporate $DAYJOB, I'd keep the history just to be sure.