Encrypted video can be easily downloaded and played. Why?

[rezahmady]

encrypt each HLS segment using AES-128 encryption works well for me, my problem is that the encrypted video can be downloaded and played on the system. This work can be easily recognized and downloaded by installing a browser extension such as Live Stream Downloader. What solution do you have to prevent downloading? And actually, when the video is easily downloaded, what is the use of encrypting it?