You might not be 22, full of idealism and hope for the future, completely distracted by high profile start up capital and valley life style. As someone who was recently interviewing in SF, I find that the younger "nothing but my bike and my MacBook" type well geared for that. The pay is good when you don't have a family and are willing to pay 2300 for a one bedroom shithole.

Of course, I'm hand waving and over generalizing. But I'd say a large portion of the talent demand meets that transient start up life style and many recruiters probably assume that if you are in tech, that its what you want.