When I went to get my ankle looked at and verify it was merely sprained and not something worse, they put me in a wheelchair. Most movement involved being pushed around, but I did move and maneuver some on my own and... here's the thing: what I want in a wheelchair isn't really offered by the simple standard model.
On the flip side, the only time I'd ever be using a wheelchair is at times like this when I've sprained my ankle and I generally try to never do that again, so it's not as if I have much use for a wheelchair. Especially since I'm generally just fine on crutches (though wheelchairs offer to vitally important things: a lap on which you can put stuff, and the ability to rest when stopped.*)
Those who actually use wheelchairs enough for wheelchair design to actually matter for them have not seen fit to make the kind of wheelchair I'd make. So it seems likely that there isn't much call for it. In fact it seems likely that the only person who would be interested in the wheelchair I'd like to design would be me, and I'm not exactly planning on being in a position to ever need to use a wheelchair much.
And yet, I think I want to design a wheelchair.
Part of it is probably just trying to make something in my mind into something real. Could I do what I want while keeping the design relatively simple and light? Would the mechanisms in my mind actually work the way I'd want them to?
Anyway, random thing going on in my head.
* Here's something I'd forgotten about a sprained ankle: your good foot never really gets to rest. You can lean on the crutches heavily and balance with your sprained foot in order to lift the good foot off the ground, but that can be worrying because you're using the sprained ankle to keep you up (even if you're taking most of the weight off of it) and it feels like the sort of thing you don't want to do for long.
That said, it is a load bearing sprain that I have, and I'm doing around the house movement without the crutches at all, so it's really more of a confidence issue than an actual necessary effect of having my ankle sprained.