I am Catholic.
Having “no problems” with your neighbors does not mean that you borrow things from them. As a matter of course, I do not lend or borrow items. This does not make one anti-social. It is well known that good fences make good neighbors.
Convenience stores are there for convenience. They are there so that society (not just myself) can use them when they need. They are there to fill the gas tank for the generator when you haven’t had power in 3 days. They are there to fill the gas tank for the trip home from Grandma’s. They are there to get Immodium and Gatoraid when your family has the stomach flu and you’re out of medicine. They are there to pick up sundry items when Aunt Suzie decides to descend upon your house with her brood.
And yes, they are there to get milk.
I would suggest you do some soul searching of your own regarding your black-and-white thinking. I’ve worked convenience store jobs and while there was a good number of people who just went because they felt like it, there were often a number of people who came because there were no other places open—late at night or early in the morning—and yes, even on holidays.
It is good that persons like you cannot be judge and jury for society. It is good that the Catholic Church understands that life happens. The hubris to sustain one enough to think that gas stations shouldn’t be open is astounding. Clothing stores, craft stores, even restaurants—they are all unnecessary. Things like gas stations, pharmacies, and hardware stores (if you’re a home owner and had a pipe burst at an inconvient time, you’d understand) are all things that are permissible because they serve a greater societal need.