I agree with you that having grocery stores nearby is helpful, but even in neighborhoods with grocery stores close by people prefer buying the unhealthy options because it's cheaper, easier, and tastier.

I think a lack of knowledge, interest, and time to plan and prepare healthy meals is the bigger issue. People don't need to go to the grocery store everyday to have fresh food at home. I only go shopping 2-3 times per month, and eat all home cooked meals with a heavy emphasis on fresh fruits and veggies.

Fresh lettuce, avocados, bananas, mushrooms, and berries last at least 1 week.

Bell peppers, tomatoes, zucchini, celery last at least 2 weeks in the fridge

Apples and carrots last 3 weeks.

Onions, garlic, sweet potatoes last 4 weeks not refrigerated.

Meat and fish: fresh can last 1 week, frozen for months.

Milk: 1 week for fresh or months if you get UHT milk.

Cheese: lasts 2-3 weeks.

Rice, beans, frozen fruits, frozen veggies: lasts months.

Eating fresh, healthy meals doesn't require a daily grocery trip. At most once a week, and with some planning every other week. I really think it's that people can't/won't handle the cognitive load of meal planning and preparation.