british sitcoms and the swinger trope... why is it always car keys in a bowl

literally every british sitcom from the 70s to like 2015 has had the same scene. neighbour invites everyone round, theres a fondue, somebody drops car keys in a bowl and the audience goes ooooh. like... mate weve never done car keys. i dont know anyone whos done car keys. its an american 1970s suburbia myth that british tv just kept recycling. only fools and horses did it, keeping up appearances had a hint of it, even peep show flirted with it... why has british tv never moved past this single gag in 40 years...