SIA's CEO replied publicly once that young and attractive SIA stewardess is a key business competitive edge to SIA has over its competitors.

Personally I find that a little degrading for the female population - your looks and your youth are being utilised for corporate gains. When you run out of it, out of the door you go. I am not sure about this, but I have heard that all SIA girls are not on permanent employment terms with the company but rather contract basis. Upon contract ending, see if you are still pleasant and pretty, we see how to work out your contract...

I just flew on Air France two weeks ago. I found myself missing SIA plane when I was on Air France plane. The reason was the service standards. I wasn't missing the SIA looks really. Well then again I am a woman. Perhaps the male counterparts feel differently.