Most likely you have either: a) already done manual labor (for yourself) or b) will and your parents may have shown you how in anticipation of this.
Or you have seen your parents do it, and have therefore seen them hold a hammer and through that learned how it is to be held and used.

I wonder if these people have never had any of the three happen. How rich does one('s parents) need to be for that?

Being a rich failson is doing that to people.