I agree with everyone else: LW skews young (also researchy; not many PhD students are rich) and many LWers care more about other things than about getting rich, and in fact the LW population is wealthier than you would expect from age alone (though I don't know how it compares with what you'd get if you looked at, say, age, family's socioeconomic status, and IQ).

I'd add: getting substantially rich takes luck as well as skill and hard work (some rich people will claim otherwise -- but they would, wouldn't they?).