This is such a serious and inportant subject, yet in Britain for some strange reason any mention of anything to do with bowels seems to be cause for merriment. It is not funny to the very many people (of all ages) who suffer from problems.
I had Ulcerative Colitis for ten years, my 'going out' anytime, anywhere, was subject to toilet facilities en-route and where I was going.
I had (have) one of those cards mentioned, never had the guts to use it. For the past 35 years I have had an Ileostomy, do use accessible (disabled) loos as it there is any problem need to have a wash hand basin available.
One of my g.children, had a problem in that the nerve endings in her bowel did not work, so she never knew when she needed to pass a motion. Her Mum often got sworn at when she emerged from an Accessible Loo with - what appeared to be a very healthy and normal child. But of course, she often needed total cleaning up and change of clothes.
Fortunately, she grew out of this in puberty - the hospital she was under had said this often happened with this condition (but not always).
The lack of public toilets, and the locking of many of those that do exist early in evenings, etc. is a disgrace and causes people with any sort of problems refusing to leave their own homes, which leads to mental health problems etc.