Netflix may push a lot of data, but people have paid ISPs to receive that data. Where that data comes from is largely irrelevant, total bandwidth matters. ISPs are trying to double charge for one service rendered.
Younger folks might not be familiar with this, but do you recall when cellphones were first starting out? If you made a long distance call (a concept totally foreign to many kids today), to a cellphone, you were being charged for the call as well as the recipient. Same if it was cellphone to cellphone for the most part. The same was not true if it was landline-to-landline.