Some billionaires may, but at least in the US this often isn't true. Off the top of my head, the Collison brothers or Sergey Brin don't need the US in any fundamental sense; they weren't born here, but came here because they thought the US was a great place to build a valuable business. If we decide that we don't like this as a matter of policy, maybe the existing crop of billionaires will be too enmeshed to leave, but the next set of foreign entrepreneurs with billion-dollar ideas won't show up in the first place.