Because they have a hard time puckering their lips the right way.
Because they're always trying to find the x. They don't know y, either.
He heard the ref was blowing fouls
Got stacks of em! First one's on the house
She only puckers up for her pacifier.
His lips are moving.
They are sitting on their lips!
Because dogs can't whistle. (X-post from r/dadjokes)