Same as it has always been. Tubes = lots of shit traffic that give some sales. They devalue the industry and are in place for pathetic program owners to gain scraps at the same time killing their own business by teaching people that "porn is free" attitude. If tubes could only have a few videos from each website or be promo clips it would be a totally different story.
If you give your content away for free don't be surprised when nobody wants to buy it.
