Older people do drop foods and change diet in response to other things that change with age, like allergies, dentition, digestion, blood pressure or diabetes. Old people aren't just young people with years you accumulate stuff and change your life in response.
I heavily doubt that's the main reason for this difference, but old people diets are a healthcare trope for a reason.
I heavily doubt that's the main reason for this difference, but old people diets are a healthcare trope for a reason.