The 6'4" 320 pounds of pure muscle could easily carry a child or someone from a wheelchair down stairs. The problem is that nobody goes to him, explains the situation, asks him to help out and coordinates.
Spend some time in a wheelchair and you quickly learn not to try to judge how cooperative the guy is but whether there is a wife with him, or better yet a girlfriend, or best of all a date. No matter how unenthusiastic he is he'll help as soon as he extracts her elbow from his pancreas...
In all honesty I've learned to wait for guys with dates to open doors etc even when it's awkward & inconvenient: you can tell at a glance if they want to score a cheap brownie-point with the girl. It sounds silly but it happens a couple of times a month.