Stand Up if You Don't Fit

So, I'm on the train one day and this lady literally tries to squeeze herself in a 2inch spaced seat between me and another female. Now in this case I clearly had the "-_-" face; however, I simply got up and told her "You can have it, it's not that serious" Seriously? OK, NYC Tip#1 if you don't fit, don't sit. Simple as that. Why must we act like we haven't seen a speck of blue (or any color) seats on the train in our life? Must humans act like they will die without a seat? AND TO TOP IT OFF, as soon as I got up from the seat to provide the obnoxious late30-looking female comfort, another lady sits on the edge of the chair. She barely fit, but I guess she felt she did. I really do not see what the big issue is. I must be Malinformed because I am not getting the point. That was just one annoying morning, and that is my #1 pet peeve to top it off. NYC, the city that never sleeps and clearly that doesn't like to stand. I guess since they can't stand it, they sit?