Small "mom and pop firms", like inner city grocery stores, sometimes exist even though they do not earn economic profits. how can you explain this?

Inner cities are identified as the central area of a major city. It is mostly composed of multi-floored townhouse and apartment buildings. Thus, its population density is quite large.

Small "mom and pop firms" thrive in this community because they are conveniently located in the hub of the inner cities. People who live in this area usually do so because they find it easier to commute to work. They would rather buy their food and staples in stores nearest to their place rather than brave the traffic and worry about parking spaces when they go out for groceries and such. 

Added to their location, "mom and pop firms" also give out family bonds to their customers. They build rapport and look out for each other in their community.