The more closely you look at Beats, the more they make sense as a serious asset to a consumer electronics company, and the less plausible the "Apple just needed to get a streaming service off the ground" story is.
Two more angles to consider:
* Owning Beats puts Apple hardware on the heads of a huge fraction of every mobile user, whether they use iOS or not. Having a Beats brand affinity for those users makes it easier to introduce new products to them.
* Owning Beats gives Apple access to Beats sales channels; whatever retail real estate Beats has is now controlled by Apple.
Two more angles to consider:
* Owning Beats puts Apple hardware on the heads of a huge fraction of every mobile user, whether they use iOS or not. Having a Beats brand affinity for those users makes it easier to introduce new products to them.
* Owning Beats gives Apple access to Beats sales channels; whatever retail real estate Beats has is now controlled by Apple.