I agree that pop-music is precisely about creating "feeling and atmosphere", but I would extend it by saying: "easily, quicly and widely accessible shared feeling and atmosphere". And it is precisely this requirement of easy/quick access to the shared feeling and atmosphere that makes it important for pop-music to be conventional, to be repetition of previous pop-music. Surprise is anti-thetical to the purpose of pop-music.
Pop-music is acoustic wall-paper that is intended reliably to create a certain atmosphere.
You can gauge the conventional nature of pop-music from the fact that you can reliably determine the genre (e.g. House/Techno, Rap, Metal, Folk etc) by sub-1-second snippets. All successful genres have signature sounds for enabling quick identification. You can think of this as an aural version of branding. This is very well-known by professional producers, musicians and music marketing.