why not

why not

1. Why is that not the case? What is the reason for your negative statement? A: "George has decided he's not going to join." B: "Why not?" A: "I don't like coconut." B: "Why not? Because of the texture?"
2. Yes, because there is no good reason to say no. A: "Would you like another glass of wine?" B: "Sure, why not?"
See also: not, why
Farlex Dictionary of Idioms.

Why not?

 
1. Lit. Please explain your negative answer. Mother: No, you can't. Mary: Why not? Sue: Could I have another piece of cake? Mary: No. Sue: Why not? Mary: I want it.
2. . Inf. I cannot think of a reason not to, so yes. Bob: You want to go to see a movie next Friday? Jane: Why not? Fred: Do you feel like wandering over to the bowling alley? Tom: Why not?
See also: why
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

ˌwhy ˈnot?

(informal) used to make a suggestion, or agree to a suggestion: ‘Why not go and see a movie?’ ‘OK.’ ‘Let’s go and see a movie.’ ‘OK, why not?’
See also: why
Farlex Partner Idioms Dictionary
See also:
  • (I) hope not
  • hope not
  • not for a second
  • not for a minute
  • not for a moment
  • aint
  • ain't
  • not for a/one minute/moment/second/instant
  • not for a instant
  • not by any means
References in classic literature
"Why not start counting at a half of one?" asked the Saw-Horse, abruptly.
The Marvelous Land of Oz
Why not still proceed over the untamed yet obedient element?
Frankenstein
"Then," suggested the idea, with a blush for its own absurdity, "why not go on pilgrimage and seek her?
Quest of the Golden Girl
But dreams--of those who dream as I, Aspiringly, are damned, and die: Yet should I swear I mean alone, By notes so very shrilly blown, To break upon Time's monotone, While yet my vapid joy and grief Are tintless of the yellow leaf-- Why not an imp the graybeard hath, Will shake his shadow in my path-- And e'en the graybeard will o'erlook Connivingly my dreaming-book.
Poems
Why not break out at her on the spot and have it all over?-- give it to her straight in her lovely little lighted face?
Turn Of The Screw
"Why not?" said Natasha, without changing her position.
War and Peace
The Why Not Inn has been owned since last October by Dave Cooper, whose The Black and White Pub Company runs 10 pubs, mainly in the Black Country.
dining: Why not hitch up at this Grand old pub?
Why Not is also about to team for the first time with Britain's Ken Loach for a film based on Gallic striker Eric Cantona's soccer glory with Manchester United.
Why Not collects helmers
Where drugs may not be available, why not use the natural approach to curb postpartum bleeding, namely, encourage breast-feeding?
Say no to drugs
So why not be all three, why not be a Hindu, a Muslim and a Christian?
Risking the better story
Why not say the opposite, that they should be kept separate.
Ed White bares all
Why not spend all the money APSP receives on member benefits and promotions every year?
Why form IAF, APSP?
Why not make civic engagement a test of individual citizenship?
Expanding the meaning of corporate citizenship: involvement in communities must reach a new level of achievement
And while you are there, why not go through the Professional Development Series?
AFCA's PDS: building better coaches
(One of art's dirty little secrets, said Koolhaas, was that it doesn't like competition.) Why not display the building's history rather than create yet another iconic venue?
Koolhaas and cultural contradiction