There’s something very noble about helping out a parent in public. I am more than willing to stand on the subway so that a mom can sit next to her young kid. It’s one of those things that doesn’t cost me anything, seeing that I have two working legs that can easily stand up over the time it takes to get from Graham Street to Union Square. However, I understand why many parents don’t ask people to stand up so they can sit down with their kids. Childless people are often very hostile towards the idea that parents receive special privileges in society, and many parents are sensitive to that. Not to mention the fact that some people have invisible problems like knee pain that make them more entitled to a seat than someone who happens to have a child. It also feels much better to offer your seat to someone who hasn’t asked for it. When it’s demanded, you’re less willing to give it up.