I don't think most developers have ever administered proprietary software so they don't really "get it".
A developer mindset sees having source access as about developing the software. For an administrator, though, having source access is the difference between fumbling in the dark and looking like a fool (or paying vendor tech support to act like a fool for you) versus being able to look at the code and understand what's happening when documentation doesn't agree with reality, etc.
Many of us are forced to integrate proprietary software. We have to live with the compiled artifacts we're given (for "support" reasons, because license agreements say we can't reverse-engineer/decompile, because we want our Customers to have systems that aren't one-offs that can be supported by the "next guy", etc). When I'm stuck fighting with proprietary software and unable to see the inner workings I find myself pining for free/open-source software.