One of the main reasons we open source is to help fix bugs by crowdsourcing our development. No matter how big the organization is it cannot have enough resources to tackle all issues with closed/ private repos and deliver value in time.
For many popular projects its a win-win situation as contributors see their name in there and organizations improve their solutions almost for free.
Everything else is politics.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.