Being recently in the market for car tires I say that some standardisation benefits the consumer and reduces waste. There are so many sizes of tires that you have limited choice on purchase and resell. Unfortunately there is no incentive for companies to standardize because they loose revenue. Apple can make a custom port and sell an overpriced cable and adapter for it. Maybe it's slightly better but is it that much…
Car tire sizes are designed for specific wheel sizes (diameter and width), which in turn are manufactured on criteria such as arch sizes, break disc and caliper clearance requirements, engine power, steering mechanism and suspension setup (for offset) and of course looks. Car wheels are interchangeable to an extent but you have to maintain same diameter to keep speed measurement accurate, so bigger wheel results in thinner tires for summer for example, and smaller, cheaper and uglier wheels for winter season where you risk curb damage, but then smaller wheel - taller tire. We would have to give up the massive car choice amounts we have to standardise here so I'd say not a great analogy.