True, facts can't be copyrighted. That's not the problem.
The effort to collect and describe these facts, and therefore the resulting work (i.e. the database) can be. The only question is which license one puts them under.
OpenStreetmap has traditionally used CC-BY-SA, but that's inconsistent. Databases are not a work of art, and the "Oslo is the capitol of Norway" entry in the OSM database is not a Wikipedia article.
The problem is: CC-BY-SA and the actual and/or intended use of the data conflict in a few places. Many people (around 85% of the OSM contributors, AFAIK) think these are important and have therefore voted for replacing the license with one that's tailored for databases, while essentially granting the same freedoms.
The "maps are facts and therefore not copyrightable" idea may be cute in theory, but the real world doesn't work like that. The commercial mapping companies out there have repeatedly prevailed in court against people who simply placed a "here's how to find me" map image on their homepage.