We're up on the hard preparing for the summer season, and just saw a
cruising boat with a lightweight steel cable connecting the aft bottom
corner of her keel to the forward bottom corner of her skeg (on which
the rudder is hung). This is clearly to prevent lines from lobster
pots or nets from sliding up behind the keel and fouling on the prop.
It seems like a great idea, but if it's good and so easy, why doesn't
everybody have it?

In short, what am I missing here?