As part of my previous thinking around copyright, I came around to the value of per-file “hey, I’m part of a project using license X” statements, as promoted by efforts like https://reuse.software.
The main reason against it IMO is the hassle, so I once again ignored xkcd: Is It Worth the Time? and wrote tec/headlice: Automatic license headers, and other licensing utilities - Code by TEC, which entirely handles it in the background.