From Longman Dictionary of Contemporary Englishwhy doesn’t somebody do sth?why doesn’t somebody do sth?a) (also why not do sth?) used to make a suggestion Why don’t you bring over a video for us to watch? Why not relax and enjoy the atmosphere? b) used to say angrily that someone should do something Why don’t you mind your own business? → why
Examples from the Corpuswhy doesn’t somebody do something?• Why don't you give me your number, and I'll call you.• Why not have the picnic in Glendale?