Why develop yourself when you can acquire others to do the development for you? That's basically been both how Activision and Microsoft have run their game development systems.
Yes, and how Apple made their cell OS. Acquiring someone isn't a subsitute to R&D and I'm surprised you're alleging that. Acquiring people isn't a bad thing. It's a form of R&D. Why reinvent the wheel, so to speak? If you can acquire a good team cheaper than building one why build it?