I can't believe you've never come across a hot dog stand that only sells hot dogs. In general, restaurants don't have a lot of regulations other than for food safety. Almost everyone has experience with them because they're so common so there's a large market size from all directions. Transactions are simple, quick, and straightforward and involve high levels of information from all parties. You know exactly how much you paid, and how much you enjoyed the item. The restaurant knows if they're making money off of those items or not. In short, restaurants are one of the most efficient markets out there, and you're unlikely to find a significant improvement that most successful restaurant owners have never heard of.