The government (usually the military) makes the thing with a basically unlimited space and budget, the private sector let's you buy one. Making an iPhone is not trivial in the slightest, too.

Also, the military (for the most part) pays for these inventions, the actual research and manufacture is usually still done in the private sector. That doesn't have to be the case, but if we take the Soviet Union as an example of an alternate system (Basically state-owned design Bureaus) they could just about keep up with the pace of technological development (and match in limited scope) but their populaces didn't see the "trickle down" technology.