Although space constraints can be a real problem, it doesn't mean that it all goes out the window. Things like the height of seats/handholds in public can be varied.
Accessibility for wheelchairs is hard, because they require quite a bit more space than a single human being, BUT we're talking public spaces, where lots of people are.
e.g near my parents there's a new health center, car park and shops being built, including a physio. It's intended to be used by families, elderly and sick people of the area. They have put in the minimum number of disabled parking spaces. In fact, there could be 8 people needing a disabled parking space at the same time and the doctors could cater for that, but there are only 4 parking spaces for them. So - person with a blue badge drives to their doctor's appt. and then cannot park.