Giving up your seat on the MRT

Yesterday I was on the MRT heading to the opposite side of the country with my room mate, as it was a long journey I was in a world of my own. Until my room mate said to me "Why is no one giving up their seat for that old man?" (we were standing in between the carts). So I looked to my right and there was an uncle in his 60's or 70s standing in front of a "priority seat" and holding onto the rail. The "priority seat" was taken up by a young female probably in her mid to late 20s... she didn't look pregnant, nor was she injured in any way... she looked perfectly healthy and probably should have given up her seat. After all the priority seats are encouraged to be given to the elderly, the pregnant, those with kids or the injured.

The woman in the priority seat actually got off a stop or two after the uncle got on the MRT. So of course she could have easily sacrificed her seat for 2 to 4 minutes?!

I remember reading in the paper once that this one person travels by MRT everyday and they have never seen anyone give up their seat for an Uncle or Aunty in their life. On the other hand, on many occasions I've seen people offer their seats to the elderly on the MRT. I've even been offered a seat by someone after they saw that my left foot/ankle was swollen and thought I had an injury, which was incredibly nice! Maybe the people that travel on the NEL are just nicer? Hehe.

Perhaps there was a diffusion of responsibility yesterday, or maybe Singaporeans aren't that nice after all, or their lazy, or their kiasusm reached an extreme as to where they got their seat and refuse to give it up?????

So here's the question, when should you give up your seat on the MRT or bus and to whom?... Actually maybe it should be what makes you give up/NOT give up your seat?