1. Apple's market share is a lot lower than Android worldwide but since Apple's customers are disproportionately wealthier with a higher willingness to spend, it would be suicidal for Spotify the iOS user base - especially in the U.S. If Spotify degrades iOS users service that will just push them to Tidal, Apple Music, Rhapsody, etc.

As far as getting exclusive content, do you really think Spotify has either the money or the marketing power to out compete Apple? Apple can market a musucian both on iTunes (pay per song) and Apple Music. The only way you can listen to a certain artist on Spotify is by paying a monthly fee - the free service will only let you shuffle a playlist.