If you're Joe Kennedy Sr. and really want to prove your family's as good or better than anybody else's, and you have millions available to you, and you stand no chance of getting elected yourself, you might commit yourself to such a long range strategy.
If you're Hillary Clinton and the presidency is in sight for you and there's no guarantee that your daughter is any good at politicking, and she may not even want the hassle of holding high office, you'll probably follow more of a short range strategy.
FWIW Jackie Kennedy might actually have managed to get herself elected to something if she really wanted it. Betting the mansion on Caroline's getting elected wouldn't have been a smart move. Not that Hillary is Jackie, but Chelsea may well turn out to be Caroline.