The rip off the band-aid shift isn't just about making the leap to a better universal connector, it's also about kickstarting the peripheral market. Manufacturers of peripherals heavily optimize on the short term, so if USB-A is still around, they'll keep their R&D low and just pump out more of that. Moving to USB-C in one fell swoop creates instant demand and forces them to move.

Apple is one of the few companies that can act as a market maker, bringing tons of consumers with money over to a new technology. The strategy was sound, and worked in the past (see iMac's USB in 1997, iPod connector, and lightning connector), though I think USB-C proved a bit too complex for many peripheral manufacturers to put out good products right away. These days though there's a ton of great USB-C peripherals out there.