Well the thing is, while our social systems how changed, our biological methods of picking a mate have not. Our genetic make-up compels us to find an strong attractive mate that will produce strong attractive offspring.
But the point of evolutionary biology is that the species on the whole will tend towards mates that provide the greatest chance of success in their given circumstances. Physical strength is no longer the priority it once was.
Organisms generally (yes, I am generalising) want the best outcomes for the minimum effort. In the case of humanity in this day, which section epitomises the manifestation of that desire to the most obvious extent? The celebrity class. Thus that lifestyle is very appealing to a great many people, as are partners from that class.
The problem is that although celebrities are successful in this current society, they really contribute little of true substance to it. It is those with intelligence, wisdom, and to a lesser extent, strength, who are best equipped to do that; but because all those paths require greater effort than the path of celebrity, they are less desirable to the individual.
Once again it is an example of people acting entirely selfishly, with no thought for the good of society as a whole.
I'm not saying that is true, however our original biological make-up has not changed much since more primitive times when survival was based on size and appearance. That is why we still tend to focus on appearance and physical strength than intelligence which would be a greater asset in the modern day society.
Well considering the the only reason humans even interact is to protect themselves (Of course, this is at the very base of all social interaction and it's a cold way of looking at things), it isn't surprising that their concern extends only as far as their own social circle.
Our biological make-up may not have changed; but then, our biological make-up does not (and did not) intrinsically predispose us to find physical strength and what we now consider physical beauty appealing. We are disposed to find appealing those qualities that will be most beneficial to us - not our ancestors - and for the minimum effort. This is how species maximise their chances of survival. Those that don't - that is, those that continue to seek after attributes that suited the circumstances of previous generations rather than those that suit their own quickly die out.