I checked Wikipedia and it had a pretty terse definition: the sale of goods and services to consumers. I have to agree with GP that another definition seems to have been selected for the sake of excluding the App Store.
Whether or not one thinks they deserve a 30% cut, Apple definitely works to make sure the App Store can at least deliver the application to the hardware and their interfaces ultimately bring Spotify's interface to the user. That fairly reasonably fits in with "the sale of goods and services to consumers". In-app purchases are more arguable (keep in mind it necessarily uses Apple Pay) but this thinking that the App Store is not comparable to retail seems to be a little narrow-minded.
