Because they don't know the words.
or
I’m just doing it for kicks.
or
A sunburnt zebra.
or
It's called "Trump It or Dump It".
or
"The erection is rigged!"
or
He got caught peeping on a test.
or
The banana split
or
Drinking, bathing, washing, swimming, etc.
or
It’s Hans free.
or
A skunk with a rash.
or