Seems to me the value proposition for a non-user is that the users the non-user interacts with are better informed through less commercially-biased sources. Something like the herd immunity value of vaccination.
Realistically, the CBC's left leaning is a balance to all the conservative leaning of the other broadcasters.
There is value in providing content that isn't 100% profit incentivized, especially as a predominately left leaning country (relative to the USA).
The stories are different too, which might come from an incentive to provide a public service rather than a sensationalization of what is happen as a profit motive.