Do I need to be on the alert on the subway?

I’ll spare you all the lengthy rant, but to my great annoyance today I got publicly humiliated by a woman on the subway who thought I was an entitled millennial for not giving up my seat to an elderly gentleman whose presence I had genuinely not noticed.

I read on the subway and I tend to get quite lost in my books. My commute is long and reading is the one thing I have to make this time into something more than a waste. In order to not be a subway asshole, do I need to be looking up at every stop to make sure there isn’t anyone around who needs my seat? I’m not awesome at social cues so I’d like to know how other people manage themselves on the subway.