I imagine non-core-product teams at Google are encouraged to submit purchase requests for any tools they think would improve their processes instead of being constrained to existing solutions. They also could just be showing it because someone with an @google.com has a paid account, but I don't know for sure :)
I would think that it also brings the advantage of having tried the actual product in their own ecosystem, Google have a good overall insight into it in case they want to buy it - not sure if this is actually the case though.