As an able-bodied 41-year-old man, I give up my seat for someone else. I do this not only because it is good manners, but also because the best way for me to teach manners to my kids is to model that behavior for them ... more so than hearing my words, they will learn life lessons by observing my actions.
OK, so now you know what I DO ... however, I FEEL very differently.
It is the HEIGHT of self-centeredness and rudeness to get onto a bus KNOWING that there are no seats remaining and that you expect someone else to stand so that you can sit. It's just plain rude to feel that entitled. It is ill-mannered to EXPECT a favor ... it's great to receive one, but to EXPECT it and feel wronged when it isn't granted? Just plain self-centered and rude.
Like I said, if I see a lady with a baby standing, I'll immediately offer my seat to her. I won't wait for her to give me "that look" ... I'll get her attention and offer it to her.
She has my assistance ... but she does NOT have my respect if she EXPECTS my seat ... in that case, she's just rude.
On numerous occasions, I've held my family back from boarding a SRO bus, electing to be first in line for the next one; we just step aside and tell the people behind us to go ahead of us. If I want my small kids to have their own seats, since I believe it unsafe for them to stand, then I will damn well MAKE SURE they have seats, rather than entrusting their safety to the kindness of strangers. The only people responsible for keeping my kids safe are my wife and me. If I DEPEND on others and HOPE that they will comply and help me keep my kids safe (by offering them seats), then I am being a bad parent because I am entrusting my kids' safety to HOPING that someone else will be nice, rather than ENSURING their safety by waiting a few minutes for the next bus. Been there, done that.
I know I'm using strong language, but also remember that I will offer up my seat without being asked ... but if the person who gets on an SRO bus EXPECTS me to give them their seat (versus is hopeful and appreciative), that person still gets my seat, but loses my respect.