I never understand why streaming services that work on subscription push some content over others. I would think if they have a monthly subscriber they wouldn't

I never understand why streaming services that work on subscription push some content over others. I would think if they have a monthly subscriber they wouldn't care what that subscriber is streaming as long as they are streaming. I find this especially bad with video streaming where a service has a great library but only promotes about 30 titles all categorized under different genres. I suppose they save on bandwidth if they can get everyone to just stream the same titles.