Because that is effort every person who uses the file has to do over and over again, whereas maintaining the file is effort that has to be done once by one person.
Someone here commented to use git blame to find the commit that banned the functions and read the commits. These people making the suggestions.. must hate other people and their time. Also, what if someone.. for example runs a code formatter on the file, making git blame useless? Is it really so difficult to make a manual or explain properly in the comments about what replacements to use?
It sounds like you want a manual. Personal preference I guess. The maintainers seem to have decided to keep it in the history. It's not like this was ever meant for anything other than git itself.
