I do think 5-10 minutes by car is really bad benchmark, but I think a lot of people do feel like that's tenable.
I've lived most of my life in places that are 5-10 minutes by car from a store, and it makes for a very isolated social experience, but also it means that if I don't have a car, getting groceries is a planned 1.5 hour experience.
Now that I'm living within walking distance, I buy a majority of my food multiple times per week, only for a few days at a time, which means I can also go to the coffee shop and see people doing the same thing, have a talk with them, socialize etc..
Another answer that assumes "close" is synonymous with "close by car".
>Given that, why would I want to go to a store that has smaller selection and higher prices, if I can get to a proper one in 5 minutes?
Because you might not have a car.
For example, I live in Seattle, in a single family house in a single family house neighborhood. I have 3 large supermarkets within 5 minute drives, and at least 6 within 10 minutes.
Given that, why would I want to go to a store that has smaller selection and higher prices, if I can get to a proper one in 5 minutes?