Cambridge is just an example, and in fact most of the initial mapping was done by a man with a job. Most of the UK now has excellent OSM coverage.
Mapping is the canonical example of something that is better crowd-sourced than done commercially. Getting data from official sources is about governments providing data in open formats.
I sometimes wonder why you post here - you don't really seem to believe in the idea of collaborative effort or free software at all. You just keep telling how much better commercial OSes and commercial map providers and massive phone companies are, when the point is that those entities can use and contribute to open data and free software too if they want and we all get better stuff.
Where are these places where the OSM mapping data is poor? I'd expect such places to be getting quite thin on the ground now. Clearly there is more data to add to OSM so that it is good for all purposes (such as motorway lane details for turn-by-turn style nav, speed restrictions) but no doubt that is all ongoing at a rate of knots.
For the last Debconf (in Bosnia and Herzegovina) it was notable that so far as Google or Deutsche Bahn were concerned the place was empty and devoid of roads or trains. OSM had excellent detailed mapping. That seems to be true for many 'lesser' countries where the big providers can't be bothered.