why not?

When my dad was traveling a lot for work, it meant a lot of late night trips to the airport for a dad pick-up.

A particular favorite pick-up was the time Noel "Paul" Stookey walked off the plane ahead of my dad.

GrammaNora: Paul Stookey was on the plane with you!
Grandpa: yes.
GrammaNora: did you sing the zoo song?
Grandpa: no.
GrammaNora: why not?
Grandpa: Honey...

Later at the baggage claim:
GrammaNora: there he is again. Should I ask him if he wants to sing the zoo song?
Grandpa: Honey... No.
GranmmaNora: oh, come on.
Grandpa: let's go, I need to get some dinner.

Even later at Wendy's:
GrammaNora: Paul Stookey's here! It's fate! I have to do it.
Grandpa: oh, god.
GrammaNora, but not to Grandpa: I have this urge to sing the zoo song.
Paul (of Peter, Paul and Mary): well, why don't we?
Both (in perfect harmony): mama's takin' us to the zoo tomorrow, zoo tomorrow, zoo tomorrow. mama's takin' us to the zoo tomorrow and we can't stay all day.