As opposed to bash scripts documented in a README file, that will be understood by more people and not have to deal with the quirks of make?

INSTALL is also a standard location, for the commands that are related to building and installing the software.

Yes.

With a Makefile I can generally just run `make` or `make <tab>` to have a feel for what's available. It's right there on my terminal, which is usually the first thing I interact with when I open a repository. If enough of the engineers use it, it stays up-to-date as it gets fixed and updated along with any other changes.

Documentation OTOH has a tendency to be forgotten and left for dead. IME this is especially true for internal documentation, and the closest to the code the docs are, the less attention they receive - since higher level documentation is more likely to be consumed by people outside of the team.

With a README, I need to:

* remember to read it * trust that it will have the information * trust that the information is up-to-date * finally, figure out paths to scripts, arguments and/or copy-paste commands