I can't see today's Brutus and Gladys sitting underneath a tree like this. Not because they are no longer in love but because that's now how their bodies work. The years have been hard on them, as they have been on all of us.
You go out and mow then if the yard is so disgusting to you.
Besides, even if they did have a homeowners' association, they wouldn't just tell you to cut your grass, they'd hang your first born over the street between the trees as a warning.