I don’t think there is a proper way to ask. Leave people that are eating alone so they can enjoy their meal. Even if you ask nicely, you are still putting pressure on the person eating. If you need to be seated a specific time go to a restaurant with reservations.
I don’t know for sure but I assume of it is because light roofs require more maintenance to look as nice. Nothing shows up on a dark brown or black roof. A white or light grey would show dirt and debris. I don’t want to waste my time washing my roof because my HOA doesn’t like the way it looks.