Well, actually, me and my wife quit eating beef and eating more turkey, fish and chicken because it is less fat, and more healthy for you. I don't even miss beef.
That's fine, but it should have no bearing on pricing measures. The only valid way to have a statisically significant tool, is to measure the same items over time. Substitutions that may be made by some to offset higher prices does not change the fact that those prices are higher.
Govt. has a major vested interest in keeping the CPI numbers low. It makes GDP look better and lowers payouts to Social Security recipients, among other things. It's like having the fox guard the hen house.