If more people subscribe to Netflix, that’s great for Netflix, but somebody has to pay for all that additional infrastructure necessary to carry Netflix movies across to Internet. And it sure isn’t going to be Netflix under Net Neutrality.
You might want to take a look at this: Netflix got worse on Verizon even after Netflix agreed to pay Verizon
If I buy bandwidth I expect to get that bandwidth all the way to the Internet. When Netflix buys bandwidth it's the same story. The Internet is the network between the ISP networks. The service providers are supposed to joining peering arrangements on those networks; they should exchange packets between themselves and settle their own costs without trying to tax other folks customers. If they route packets across their network from one isp to another, that's between ISPs, not ISP customers. Their peering agreements cover this issue.
Outfits like Verizon are just trying to exploit their customer base as an asset by charging an extra tax on certain packets. If they truly didn't provision enough capacity to handle customer commitment, especially after locking all those customers into contracts and committing to all those peering arrangements...whose fault is that exactly?
I should note that consumer ISP contracts tend to not guarantee bandwidth, somewhat in defiance of the actual advertising. I imagine Verizon executives imagine this absolves them of responsibility of ever actually delivering on the advertised bandwidth.