Unlike pretty much all other standards, all USB documents are open access and allow you to build compliant devices without 3rd party permission. You only need a license if you want to sell devices with the logo and/or need a official Vendor and Product ID (VID/PID). So unless all manufactures are forced to publish documentation for their IO in a similar level of detail, forcing one standard upon everyone is the next best option. Apple gambled on keeping their connector proprietary, and now get the backlash they deserve.