I don't think you can set aside universities when you talk about open source - they were the original drivers in this field, and continue to be heavily involved. The biggest difference is probably that most of the software written at a university is done by faculty and grad students and isn't work for hire, so for someone like me there's no reason to ever ask my employer to execute a CLA.

But the same problems arise in most other organizations - it's hard enough to get a legal department to sign essential things needed to keep a business running, never mind signing some random CLA for a project they haven't heard of.

Finally, your view seems oriented to pseudo-open source projects where someone slapped an open source license on code written at a single company and wants to keep control of that code within the company, rather than open projects spanning multiple organizations, run by the developers and architects of the code.