I don't think DRM stops them from doing P2P. Limited upload speeds are a much bigger issue. Plus people finding it icky to be an uploader on something they already paid for.
BitTorrent solved the limited upload speed problem. Split the data into chunks and download from multiple users at once. Even that is only necessary if a user doesn't have enough upload bandwidth for a stream, which for 1080p is ~5Mbps.
And the second problem has a simple solution. Give the customer a tiny discount for uploading. Anyone with an unmetered connection sees it as free money even if it's only pennies/month, and it works fine even if some customers turn it off because the discount-accepting customers can upload more than they download.
And the second problem has a simple solution. Give the customer a tiny discount for uploading. Anyone with an unmetered connection sees it as free money even if it's only pennies/month, and it works fine even if some customers turn it off because the discount-accepting customers can upload more than they download.