The reason that certain amount of cash is restricted or questionable when a minor is having it is to prevent them from going into illicit dealings like drugs, buying of guns etc so that they can be observed. But bitcoin has no boundaries, no limitations as to age and otherwise.

If you have large amount of bitcoin, you can play around with it, transacting, transferring to exchanges but once converted to fiat, eyes will be on the inflow and outflow because of certain restrictions as I said earlier, either because of age, cash transaction limiit etc.