Because 68 69 70.
Because 69 is a bit of a mouthful.
70 because after 69 your mouth's full.
There were 3 car accidents in Mexico 70 people died. What do you call a bunch of black people in a swimming pool? Coco puffs.
68, because when she turns 69 she blows a rod.
68, because at 69 she gets a frog in her throat...