Self driving right now is a moonshot for many of these companies, and competing with the resources that Google can throw at (both in terms of AI talent as well as sheer money) can be tough. Partnering with GM allows Honda a piece of this, allows for future adoption, and consolidates both of their revenues. If Cruise does become successful, the thought process might be that both Honda and GM obtain the tech therein, and differentiate themselves via other methods. Imagine this to be a new engine type that is too costly for just one manufacturer to research, and so they partner up with the implication that both get usage rights once the engine is done.
