Many bars stick to serving alcoholic beverages (and some non-alcoholic beverages), and they do so for good reason. By not serving food, they don’t need space for a kitchen or kitchen equipment, they don’t need kitchen staff, and they don’t have to worry about the high cost (and relatively low markup) of food inventory.
But there’s a benefit to serving food at your bar: it can help keep patrons who get hungry onsite for longer, and it can bring up average check size significantly.
Some bars, especially dive bars, formally or informally partner with nearby restaurants to satisfy their increasingly hungry customers. They encourage patrons to go get their own takeout and bring it back, or order delivery from a nearby restaurant and enjoy it alongside your drinks and warm service.