This will sound awful at first, but bear with me. Society / civilisation is based on rules or conventions that shape themselves around the most common use or most generally convenient to produce. Neurotypical, able-bodied people are the "best fit" as far as following those conventions goes.

So, because they conveniently fit into the world that has been generally shaped around them, they don't really have to think about how to navigate the obstacles it presents for people who don't fit as easily.

Getting on the train in the morning is just a step. I don't have to think - I just step on, sit or stand, get off.

Someone with a cane or hip issue might feel inconvenienced, but it's unlikely to put them off the journey entirely - they might change their departure time to avoid rush hour, or pay extra to reserve a seat if possible, but they'll still go.

Someone in a wheelchair or scooter is going to have to Plan and Notify and Check to make sure they have let the station staff know they'll be there, get there early in case the message wasn't passed on and to give them time to get the ramps, hope nobody will be difficult about letting them on the train and that it won't be too full to get them and their vehicle in, and get in while being stared at my bored commuters. Then they do it again to get off the train.

In addition to the time and ease differences, there's a massive difference in mental capacity taken up. It's exhausting being disabled or neuroatypical in a way most people will never really experience, but there are plenty of ways that society's conventions cause issues for people that should allow for empathy but frequently doesn't. Overweight or unusually tall or short people don't fit in average clothes or average houses, people with severe allergies of common foods have to be on alert to cross contamination and people who don't believe them, left handed people have to use tools designed to be held in the right hand, and so on.

I guess it boils down to - neurotypical able-bodied people see convenience or normality where neuroatypical disabled people see obstacle, because the world accomodates the former at the expense of the latter.