Have you ever seen a report on the news about a fire in a restaurant or similar venue where a lot of people are gathered? Usually, you see panicked people running and trying to get out, many times leading to injuries caused by other people and not the fire.
This is the reason why there are guidelines for how many people are allowed to be in a building at a time. This is called the occupancy load. The occupancy load for any building is dependent on the size of the building, the number and size of available exits and the type of business it is. A dance floor will have a higher occupancy load per square foot than a restaurant, for example.
Obeying the occupancy load for your place of business is the safe thing to do. Not only is it a danger if a fire was to break out, it could also cause your floor to collapse, leading to serious injuries, and even death.