AT&T developed the transistor, but it was government pressure that prompted AT&T to release control of its patents on the invention, and it was licensees like Motorola, Texas Instruments, and Fairchild (which gave birth to Intel) that did the bulk of the work in the transistor market. AT&T wasn't even sure what to do with it; they were just looking for something better than the vacuum tube.
The Alto was first built in 1973, but was used only internally at Xerox and was never made into a commercial product. Meanwhile, a loose-knit Homebrew Computer Club had among its members two guys named Steve. It was a visit to Xerox by one of them, in 1979 -- a full six years after the initial release of the Alto -- that led to the beginning of the modern graphical interface.
Microsoft began developing multi-touch technology in 2001, but it was the iPhone, in 2007, that won the market. Rumors of Microsoft's wall-mounted multitouch displays predate Apple's products, but it was Apple that figured out how to get the products into customers' hands.
What has happened to the PC is that it has become mature. This happens to all technologies. Modern automobiles are not very different from their 1950s counterparts -- just more refined. Refinements in PC technology however has led to things like the Raspberry Pi and a second-generation community of electronics tinkerers.
Not to belabor the point, but the automobile was also patent-encumbered, and it was the development of better production techniques (the moving assembly line, by Ford), that made the automobile accessible to large numbers of people.
The fundamental problem of product development is that those most suited to inventing things are usually not also those most suited to bring a product to market.