The POINT of Chained CPI is to create the illusion that inflation is less than it actually is. That's why they are doing it. Obviously people make adjustments to spending to compensate, they either do that or they ultimately starve. What chained CPI does is it uses these purchase changes to support the claim that prices never actually increased at all.
Let's take a grocery basket. In it is a box of Craft Mac and Cheese selling for $1. Over the course of a year that box of Craft Mac and Cheese increases to $1.49. Under any sane and objective measure of inflation you would conclude that the price of Kraft Mac and cheese has increased by 50% -- a massive increase. Enter the magic of chained CPI.
They simply find a box of mac and cheese, in this case Fukushima Select brand "Mak and Cheez" that's still selling for a buck and voila, there was no inflation. And when that goes up they do it again, and again, and again. Using this logic you can claim anything you like. You can claim chinese brown label horse droppings with extra lead and polymers are the equivalent of Alaskan King Crab.
But over time what happens is this: with every year and decade that passes the actual value of social security compensation falls further and ever further behind where it is today. Eventually the compensation becomes worthless. Worse, and this is the point of doing it in the first place, once this is pointed to younger workers -- once they understand that their guaranteed social secuirty check isn't going to buy they chinese horse droppings with extra lead and polymers -- there will be no argument against privitization.
The choice will be between a guaranteed nothing, and a chance at something. And then Social Security dies. That's it.