You still assume they collaborate to sell. My point is that people develop things not to sell them. If you just want to develop something to solve some problem

You still assume they collaborate to sell. My point is that people develop things not to sell them. If you just want to develop something to solve some problem you have, and the choices are either putting in the full resources yourself or to collaborate with someone else who has complementary expertise, then you have no reason to not collaborate. You put in a fraction of the resources but still get the full benefits of having your problem solved. Only in some extremely paranoid view of the world where every piece of knowledge you have should be leveraged does what you say make general sense. If you are Apple, for example, say you compete on design and functionality of your apps. How would it not benefit you to collaborate with other companies to develop some library or parts of the OS or whatever? Your competitive position is not damaged because you help Microsoft or whoever get the same functionality, because you're not competing on that.