Why? Google is a low-quality road map for cars. They don't put much effort into walking. In the OSM community Google is considering a very low bar. We aim to meet or exceed the quality of mapping like Ordnance Survey.
I take the parent comment to mean it's impressive that a community project outperforms one backed by a multi-billion dollar company - i.e. it's a compliment.
Yep! The multi-billion dollar company doesn't see a commerical reason to get good at walking details. Cars are more profitable. So they don't put effort into it.
A goal of OSM is to map _what we want mapped_, not what makes commercial sense to map.
Which is also a reason you'll find rural areas mapped really well in OSM and not at all in Google Maps: Why invest in a place where you cannot run advertisements?
I'm not saying OSM is more complete than Google maps, just that the incentives are different and therefore the coverage is different.