> than whatever proprietary data they licensed to get started
I detect a bit of a fallacy in what you're saying, that Apple wanting to have control over their own geographical data must mean that they aren't using or contributing to OSM. It isn't a zero-sum situation.
That doesn't stop Apple needing control, or at least feeling that way.
> Apple could as well contribute whatever improvements it deems necessary to benefit themselves and everyone else
They do. Apple uses OSM data and contributes to OSM indirectly (https://wiki.openstreetmap.org/wiki/Apple).
> It would've been a much better starting point, too
Who's to say? As stated, Apple does use OSM data. They use data from multiple different sources. (http://gspa21.ls.apple.com/html/attribution.html)
> than whatever proprietary data they licensed to get started
I detect a bit of a fallacy in what you're saying, that Apple wanting to have control over their own geographical data must mean that they aren't using or contributing to OSM. It isn't a zero-sum situation.