I think that control of content is one of the major reasons for this. If users were more able to readily (and for zero cost to them) cache content when connect

I think that control of content is one of the major reasons for this. If users were more able to readily (and for zero cost to them) cache content when connected to local networks then we would see less content transferred over 'higher cost' networks. Of course streaming services (I'm thinking more of Twitch than Netflix) for live content production are 'rather difficult to cache' in their prime viewing time.