Because if you serve hard liquor, you have to maintain a 45%-55% food to mixed drink ratio (beer and wine don't count). You can't have a hole in the wall establishment that focuses on selling alcohol.

If you have a beer/wine only license, you have to sell $4,000 in food a month, no matter what. $2,000 of that must be in entrees.

Exceptions have been carved out over the years for entertainment venues, vineyards and breweries where alcohol is brewed on-premise, but these laws date back to the end of prohibition, and have basically stopped all dive bars from existing in Virginia.