I cannot answer your question, but I am responding because (a) maybe
a teacher will answer, and (b) I would feel comfortable
using that question only in this way:
Martha: Did you invite George to come with us?
Martha: Why not?
Tony: I did not think that he would like to come with us.
Martha: Why would he not [like to] come with us [if we invited him]?
Tony: Because he knows that Mona is also coming with us, and
he dislikes Mona.
Thank you & have a nice day