Are you sure about that? The vast majority (err ... all, as far as I can recall) of webrips I encounter are reencodes. You don't need access to the original DRM protected stream for that, only the final decoded output. HDCP is the weak link there. You can purchase very cheap dongles that strip the encryption.

What wouldn't surprise me in the slightest is if the widevine devices are stenographically embedding a fingerprint in the video signal and getting burned because of that. I don't have any evidence that's happening but it would surprise me if it wasn't.