Lackydaisyical - you need to read the whole thread if you think it's all about space for wheelchairs.
I'm not being "extreme" just explaining, but you said it was a genuine question.
Those of us with continence issues can often use normal loos. I certainly do most of the time. Here's your TMI alert if you are scared of poo.
WArNING - THIS POST DISCUSSES POO ON MY BODY. And it's quite long and I haven't previewed it ...
I have a colostomy. On a good day, when emptying my pouch, I merely get a few smears of poo on my hand while I do this and can manage to re-dress myself and wait until I get outside to wash my hands. Sometimes, however, the pouch which collects the poo bursts off and poo is smeared over my tummy. Sometimes it's just a little, sometimes it's lots. I need water to wash it off. Space also helps but water is essential. If the chips are down it can be done with a water bottle and a lot of wiggling around in a narrow cubicle but it's hard to do in a sanitary fashion, and it's very hard to do without getting poo on my clothes.
Of course, if I'm really unlucky - and this is very very rare as colostomies are pretty easy to manage these days - the bag can burst off getting poo on my clothes. Then I absolutely must have privacy to wash and dry my clothes.
An added complication is that I am having chemotherapy. This reduces the effectiveness of the immune system meaning I have to take extra care when dealing with poo. I'm under strict instructions from my nurses to make sure any bag changes or poo on tummy incidents don't compromise my Hickman line. We'll go on for ever if I explain what this is. But it does mean I must keep very clean. It's not optional. I spent three weeks in hospital lat year when it got infected and I don't want that to happen again.
My bowel issues are very much the easiest to deal with of those entitled to use disabled loos. My random bowel splurging is protected by my bag. It's nowhere near as bad as someone with Chron's or bad IBS. My life is actually quite easy to manage and barely affected by my "disability" at all. It's really only legally a disability rather than anything else. But even I do need access to disabled loos.
While I am an adult and can wait with poo running down my tummy, however unpleasant it may be, I have absolutely no doubt in my mind that it is easier for a baby to wait to have its nappy changed, or have it changed by its parents on a mat on the floor.