Possible reasons:
1) Conservation of energy (perhaps more of issue for outdoor cats?) The article mentions conservation of energy.
2) Food puzzles expect cats to act contrary to more instinctive behaviors (ambushing prey). Also mentioned in article.
3) Cats have human servants - why work for food? Personal observation.
My cat has an open, always full food bowl. He has unlimited access to water and a clean litterbox.
He lives to hunt. He comes in in the morning, sleeps and eats, then back out he goes to kill vermin. Unfortunately he considers taking the occasional bird part of his job.
He gets a pass, since at least one rat per week is his average. He got a whole family one evening, and actually laid them out in a row at the base of the sundeck stairs.
GOOD kitty!