Over the past year, Pietersen and Broad have gone the same way, and so did Lendl Simmons in the world T20 semi-final. It even happened in a club match I played in a while back. The reason's obvious: batsmen move across the stumps far further now than they did even ten years ago, meaning more balls hit that area and then fall correspondingly closer to the stumps.
The answer's simple enough. Why doesn't someone just redesign the thigh pad? Instead of the traditional curved bottom edge that the ball seems to catch in and roll around, just extend the pad down and taper the bottom. A decade ago it wouldn't have been worth doing, but it is now.
NB: Can the manufacturer that implements it send the royalty to this address. Cheers.