In reply to Jack Huang.

Not everyone needs to. If you're using a plugin from the WordPress plugin directory, you can click a button to update or enabled auto-updates (coming in WP 5.5). However, not all plugins are available through the plugin directory. For those, there are various other ways that users might update. Sometimes, plugin authors offer one-click or auto-updates. Sometimes, users are left up to their own devices, such as using FTP. Then, there are times when developers are working with clients without server or FTP access. The ability to upload via ZIP simplifies things where a more technical route may be necessary.