Are we all supposed to own farms? How does that work with 330 million Americans? Who is going to have time to do things like design the hardware and software that power the devices you use to post on the internet--they don't have time to do that and work their personal farm for food...
However, let's put this in context - when was the last time you did something, purely altruisticly, without any expectation of recompense? I think the people who do that kind of work are exceptional and exceptionally rare (assuming you are such a person). Even in those cases, those exceptional people choose problems where they can do the most good - and even if it can be argued that a community grocery store is such a place, it "competes" with various other local and global issues.
I imagine you need to get paid yourself in order to support your lifestyle.
Imagine someone were to approach you and ask the fruits of your labor for free - "qbasic_forever's software is a community good, why won't he simply do it for free?" I'm sure you have a variety of reasons, but most people's answers would be: life requires resources, so I must acquire those resources so that I and my family can live.
The grocery store owner and employees are in a similar circumstance. Or perhaps, a worse circumstance: "why should we continue to provide for a community which constantly steals from us and makes it harder for us to live?"
I have a very hard time answering this question - so I sympathize dearly with the grocery store owner.
Or: farms task themselves with producing food in the same way programmers task themselves with producing software.
The answer is, I don’t know why people do everything they do, but the labor market sorts itself out according to incentives, ability, compensation, laws, education, the dispersal of information and any number of factors.
We have farms and they are really good at what they do because we have food that is readily and cheaply accessible in abundance.
Why should the owners of that supermarket go into ruin just to give you another shopping option? Why is it their responsibility to keep you fed at all?
Also, shoplifting is like calling firefighters to water your lawn, because, see, it's free!
Finally, they do have charitable "food delivery" places - they are called soup kitchens, but they are intended for people who can't afford food at all, not necessarily for people who have the money to buy what they need.
https://thegrocerystoreguy.com/what-is-the-profit-margin-for...
Really many factors bring even some losses to be unacceptable.