I think the society is becoming "judge by appearance". My dad is 70+, uses Brylcreem, so hair appears glossy and black. He doesn't get a seat. Then some younger bloke comes along, probably late 50-early 60s, with fluffy white hair. Someone gives up his seat to him.
To addon, sick does not mean the runny nose, sneezing kind of sick. There are truly sick people on public transport such as those suffering from cardio disease, cancer, slipped disc, etc. We cannot tell they are sick but I am sure they also liked to be treated like the handicaps.