Just to be clear, we do not obsess about maximizing the plan. We do not like CS, we typically spend half days at the parks, and dining is a big part of our trips. Our kids consider Ohana, Chef Mickeys, and Hoop Dee Doo as important to our Disney trips as 7DMT or BTMRR. I also have "disney adults" who would prefer a filet, crab legs, or lobster to chicken nuggets any day.
The dining plan certainly is not for everyone, but there is definitely those who will either come close to even, and like the option of knowing the cost up front, or save on the plan.
I don't think anyone is saying to get a dining plan knowing you will spend hundreds of dollars more than you have to, but when the costs are about even, why should it be so controversial?