I also pay developers for a commercial licenses for FOSS offerings, if they are able, that I never intend on using because the project looked promising.

I donate thousands of dollars a year between charities and open source software, Why wouldn't I do it in the most tax advantageous way?

In most of the companies I'm familiar with, it's very hard for engineers and their managers to spend money on things that don't have a tangible return, particularly something you can stick an inventory tag on.

Marketing departments, on the other hand, are purpose-built to spend money on intangible things.

I've coached a high-school robotics program that's mostly funded out of the company's marketing budget, which they justify because the students put logos on their machines. Everyone knows we're doing it because we think it's awesome, but we have to call it marketing to slip it past the beancounters.