The reason is always the same: the content and the key that decrypts it are both present on the client’s machine. The user’s hardware decrypts the content to display it. The user’s hardware is, definitionally, something the user controls. Any sufficiently motivated person with the right tools can intercept the decrypted output.
圖像來源，BBC CHINESE/ TING CHIANG，这一点在heLLoword翻译官方下载中也有详细论述
Цены на нефть взлетели до максимума за полгода17:55，这一点在WPS官方版本下载中也有详细论述
On this macOS system, that produces 230 fonts across five categories:，详情可参考Safew下载