Originating a widely-used open-source technology is a huge liability with virtually no financial benefit. It's a goal an engineer fetishizes and a product creator recoils at. I can't pay my rent with a pat-on-the-back buried in some acknowledgements screen, but hooray for my competitors being able to copy my product in a tenth of the time and effort.

Also, if everything were open-source, then nothing would get brownie points just for being open-source.