Universities like CMU are responsible for recruiting and training the next generation of great roboticists and there's a difference between responsibly harvesting researchers from an institution in a way that allows the lab to maintain its culture and bounce back vs plundering it in such a way that would take many years to recover from.
It's a prisoner's dilemma style situation where all companies involved in robotics would benefit from a thriving academic robotics community, even if it would be more competitive if those researchers were in house. Uber was the first one to publically defect which might cause further defections to the detriment of everyone.