In 1975, the federal government passed the Magnuson-Moss Act. Ask the next 100 people you see, what this law is and why it made the explosive growth of the computer industry possible, and you will likely get somewhere between 98 and 100 blank stares.
Back in the 1960’s and 70’s, IBM sold mainframe computers, and sold a lot of them. IBM also sold service, accessories and upgrades for those systems. What IBM did not do was allow anyone else to poke around in those machines – even after the sale. IBM did not allow the machine purchasers to add in accessories from other manufacturers. IBM kept it all and kept it all as trade secret. Hence, when, in 1981, IBM introduced its take on the personal computer, the world marveled at its open architecture. The IBM PC was open. Anyone could, and did, build and sell accessories and replacement parts. IBM copied the Apple II in that respect. The infant industry had already learned from the success of Apple II, that open is best.