Because they're stuck between a 69.
I feel so enlightninged!
He was shocked.
Because Rouleaux triangles are too hard to manufacture. What do you call 8 hobbits? A hobbyte.
Because she wasn't peeling very well... All credit to my 8 yo son who suggested I post it here
Because 69 is a bit of a mouthful.
70 because after 69 your mouth's full.
Because 7 was mean. Get it?
Doctor: 10 Guy: 10 what ! 10 days, 10 months, 10 years Doctor: 9...8...7...6...5...