So they have some R&D... but how much can each company really do at any given moment? For every research project Apple or Microsoft does, how many projects are under work at $random_startup? For ever good thought Apple or MS has, how many ideas does someone come up with that otherwise would have never been considered?
It's advantageous to have both environments pumping out new technologies, obviously.
The environment at Google and MS is that they have near unlimited resources (legal, monetary, intelligence, computing, patents) to create a working product that can be mass-produced quickly if it's a success.
A large company might have some red-tape to go through, but it will also already have all of the HR and management systems setup so that project managers can focus on creating the product.
The Project Tango device for example went from concept to thousands of 100% working devices in developers hands in just 1.5 years. The low-level drivers are integrated with Android in a way that no 3rd-party startup would be able to do. The talent they acquired (former DARPA director, Kinect engineers) would have not been possible without large company resources.
Ideas are not what is important, we all have brilliant ideas that millions of other people have had. You have to be able to take those ideas and actually create a product or service that people can use.
