Have you ever noticed how many different ways there are to transport a small child? 4 wheels, 3 wheels, pivoting wheels, adjustable handles, plenty of space around the child in case of knocks and bumps, extra carrying space for your shopping...
Somebody somewhere (or, more likely lots of somebodies in lots of somewheres) has put in an awful lot of time, energy and money deciding how tiny children can be safely transported with the minimum of effort on the part of the carer.
Now look at a wheel chair:
2 bike tyres with no way to pump them up. No way to change them.
Shopping trolley front wheels.
More often than not, due to lack of mobillity, the person sitting in the chair is bigger than the chair itself.
Now, I'd like you to ponder something. How much time does a small child spend in a buggy? If the parents don't drive, possibly 2-3 hours a day, maybe less. How long does a wheelchair user spend in their chair? Dude I work with finds transferring difficult, so (apart from using the shower, going to the loo and sleeping) he's in it all day. Around 12 hours. Opinions on a postcard, please!