At some point you guys need to realise that society stops being divided into age groups after you leave school. A 22 year old and a 28 year old are both adults who can do what they want.
But why should a man stand for you to sit just because you're a woman(you're not pregnant or sick even).
That's chivalry and chivalry is based on the premise of female weakness. We cannot claim to want equality and subscribe to chivalry.