Yes, I think you are an asshole for arriving at this conclusion. Maybe they’re unable to convene and enjoy free time together as a family prior to 5pm. Maybe they’re not intimate with the etiquette of tennis. Maybe this is simply a flat, predictable surface in which they are able to have fun upon. Maybe a lot of things. It is likely more often the case in the traditional American model that mother rings the dinner bell as the sun is beginning to set, and all of the children cease their rumpus play and return home, maintaining tranquility until the next day. Maybe try to consider that they aren’t attacking you, that this isn’t personal, and that it’s just their way of pursuing the American Dream.