It's easy to blame the boss, but I don't think its the companies responsibility to give back to open source just because they use it. If you think open source is helping you, you could contribute it in your time without expectation to get paid for it. Most open source projects work like this. And if some company needs some extra feature, they should pay market rate for it.
Assuming the company doesn't have clause to not allow contributing to open source. These companies should be publicly shamed if they use any open source code.
From the many people who asks for things, only a tinny percentage are actually willing to pay for it. Take Microsoft, I had one of their employee asking me to support their azure stuff: https://github.com/mickael-kerjean/filestash/issues/180. When I found out the dude was actually employed by Microsoft, I somehow though he could give a hand, but no he was just there to make some feature request ...
Assuming the company doesn't have clause to not allow contributing to open source. These companies should be publicly shamed if they use any open source code.