Mostly because they compete in areas and as a corporation we don't expect them to help their competition.

At best they get praised for doing things in a way where they benefit or are forced to face a worse alternative without control or a hook. Whenever they seem to do something selfless the control, hook or incentive to taking in some patent comes along with it.

I don't expect to put .net stuff and the like in the same category as GNU tools anytime soon.

Is it something of CEO's past? I remember the ODF debacle, the MAUI naming , the numerous anticompetitive business practices, etc all not being far off. Hell even OEM bundling court cases are not a thing of the past