All significant open source development today is done by folks who are not "scratching an itch" but cashing a paycheck, and the projects they release are things that would not have made them money anyway. The actual valuable stuff the trillion-dollar companies of today do is still overwhelmingly closed because secrecy is still a better way to engineer products that sell.
First, I really do appreciate what you are trying to say - that proprietary software is where the money is. It also could be that most of the time, there really isn't a reason to share source code. I've built lots of software for companies large and small. Most of that software is for automating some very specific business process, or making some machine configuration work that no one else in the known universe would ever want anyway. The only developers who that code has value to will work at or for that company. It's not that it is secret, it's just a snowflake. In many cases the budget was so small, that the application wasn't tooled to run anywhere else but on that customer's existing infrastructure, so it would take more time to make that code open-source ready. BTW, open source code generally (but not always) is much higher quality than what I see in most proprietary software because it is going to be reviewed by lots of others and there is often an expectation that that code work on multiple platforms.
Also, when you use absolutes, like "All significant open source development is done by folks ... cashing a paycheck" you are guaranteed to be wrong. It is also disingenuous to people who actually are out there scratching an itch... and to all those developers who started by scratching and itch and finding customers or companies to pay them to keep scratching that itch.
