I don't think it's either of the reasons you stated. I think it's more about how many accessories are out there using Lightning that will be obsoleted by the switch. It's like the Dock to Lightning switch, but on a much larger scale simply because there are far more iPhones with Lightning (and therefore accessories) than there were with the Dock connector.
USB-C didn't even exist in 2012 when Apple rolled out Lightning. Micro USB would have been the "standard" choice, but it couldn't match what Lightning was capable of. I don't see how you can blame Apple for this.