Its because old people got nothing better to do, they can't go outside without breaking 207 bones, can't go online without getting 91 scams and 172 viruses, can't read a book without falling asleep while trying to figure out what the first word is
Sometimes my grandma calls me a glutton when I eat a lot of food at once which is rare. I don't have any vendetta or bias against fat people, but I just feel like she has absolutely ZERO room to be talking about gluttony since she's like 470+ pounds, bases a good 40% of her personality off of how much she loves food, and spends 90% of her time eating.