It is pity and fear
Excellent question !!!!
Wheelchairs going to the head of the line is an epidemic.
At Disneyworld, if your in a wheelchair, you and your party do NOT wait on line. Consequently, hundreds of ambulatory people rent wheelchairs for the day to avoid the lines.
My aunt is sometimes in a wheelchair. We went to a concert and the line was about 100 yards long to get in. I just shouted "Excuse us," and not a fool say "Why?" So we went right to the front of the line. hehehe
It is NOT right that wheelchair people don't have to stand in lines. It is only out of pity and the fear to say "no" that they get away with it. Yes, they are handicapped, but so are many people in many different ways. Why does a handicap give people the right to barge ahead of others?