I think you are missing the point. If I remember correctly, iOS will flush the cache if you want to download music, there is no need for the user to do any of this thus no need for a flush cache option. The OS will/can take care this as you use your phone. Just becasue you don't see a reson for caching, doesn't mean that others (like me) don't use it.
I really wonder about this if this applies to all kind of actions/app (photo,video,music, 3rd party apps with offline music, 3rd party offline podcasts.
I understand that there is already a cache feature and that this is well though out by Apple and is pretty good in the way it works (a lot better then Android) and that it offers many advantages for many users.
I don't say that it should be removed as it is but please give the user a bit more options to clear cache per app(s) in a way that works for the each user and their specific demands.