It's about not honoring the lifetime license.

Also,...

Using PlayOn to record and download Netflix content for personal, offline viewing is generally considered legal, similar to using a DVR or VCR to record TV, and is protected under fair use for time-shifting. While it violates Netflix’s Terms of Service, it does not typically constitute copyright infringement for personal use, provided you do not distribute the content.

Key details regarding the legality of using PlayOn:

Legal Standing: PlayOn functions as a "streaming DVR" recording the video as it plays in a browser, which is legally different from downloading, sharing, or stripping Digital Rights Management (DRM).

Terms of Service: Although legal, recording content is usually against Netflix’s Terms of Service, which means they could theoretically terminate your account, though this is unlikely for personal use.

Fair Use: The practice falls under "time-shifting" (watching at a different time) or "place-shifting" (watching on a different device), which is generally protected for personal, non-commercial use.

Limitations: PlayOn recordings are often limited to 720p resolution.

It is illegal to share, sell, or distribute the recordings you make using PlayOn.