Earlier quoted context omitted.
It started as a way to recognized important contributions to a field outside of the academic process.
The article that started this conversation, completely disagrees with you, and they cite the historical record of the early honorary degrees.
There's a difference between "first" and "representative of how a thing caught-on and came to be established and practiced" -- the first uses might not be representative of neither the reason for widespread adoption nor current use.
There are countries whose universities need (and do) no marketing at all otherwise, because they are public and state sponsored, but still give honorary degrees to honour important contributors from outside the academic field.