Why do men still prefer (youthful) beauty over (slightly) older and wiser?

Still stuck on the twenties issue...

Why is it that the climax of my life so far, i.e. being 21, was characterised by being insecure, innocent and immature, yet also allowing me to be sexy, fun, popular, wanted and hugely fulfilled?

I am beginning to accept that good looks and ignorance are what makes the world go round. Not just go round, but words like power and wealth come to mind. Just look at Tom Cruise for example. Do you see what I mean?

Here I am, ten years down the road from 21, all the wiser and so pro-damn-foundly more experienced than my happy air-head days past. I exercise more than I have ever done, I’m not too bad looking for my age (some still think I am in my early twenties), I can hold my own in any conversation (for that matter debate on just about any subject), I actually have my own opinions now and don’t feel the need to be clingy or helped anymore. Just when I thought I've finally got to the stage where I can stand on my own feet and face the world, I realise that I am not needy and youthfully attractive enough to attract a good man?? (The kind of man I attracted in my early twenties: thirty-something, slim, toned, funny, charming, well-mannered, sociable, happy, fun...)

Can somebody tell me Why is this???