It provides a reason for them not to just “take their ball and go home” once they have a pile of money.

If that’s the reason for it it’s not doing its job. Investments are much like savings to high net worth individuals and their investments are managed by someone else and they simply lay in the cut and collect dividends. Yes there is a risk to investments but if you’re in a good wealth fund then over time you’re almost guaranteed to win even if you have disastrous months here and there.