It was also done in 2016. The only reason they are paying for it now is because they are going to be on the public market so they have to be treated like a real company would. Also coinbase were doing it because everyone else in the world at the time was using the same bots 100X more than coinbase ever did, to create fake volumes and rank their shitty exchange on top of the volume chart. I didn't even know coinbase was also creating some fake volume because they always rank pretty low on volume. I guess coinbase were just testing their bots in case they wanted to do the fake volume too, but eventually decided to not compete on that front.