The rise of 29ers has proven that beardy old cycle tourists were right all along. The move of 27.5 from tourist idiocyncracy to MTB mainstream has given MTBers are slightly marginal choice at the expense of braking a well established global standard, removing the choice of correct wheel size for smaller riders.
Bike shops dont have room to stock a multitude of wheel and tyres sizes, 3 seems to be the limit. With the rise of two MTB choices, the industry has all but eliminated the small road wheel 650c and small MTB wheel.
In my perfect world, 650c and 26" would be combined into one size.
Another weirdness is that bikes are assigned wheel size according to application, not size of frame.