A vegetarian told me that this is due to practicality. When he goes to some event, why does he bring sausage-shaped "meat"? Because then he can use the buns and

A vegetarian told me that this is due to practicality. When he goes to some event, why does he bring sausage-shaped "meat"? Because then he can use the buns and ketchup that were provided for everyone. Same with burgers...