Because 69 is a bit of a mouthful.
Because it's waaay easier to swallow
The vegetable garden.
Baby! Let's do a 69.
You can't get pregnant during '69.
Me: Two. 4-year-old: It was nine. Teaching her to count was a mistake.
Dis counts!!
When you're buying salt.
General
Is that to differentiate them from the all those actresses that only play walls and bits of furniture