Why using an app client instead of just using the web version?

I really want to know some real use cases for using an app client (like Tokodon) instead of just using the web version on a browser.

I know that in some cases it's useful, just like to keeping different instances of the same program open and block cookies to accessing all your web browser, and I actually used them for some time, but at some point I realize that why I did not use the web version all the time before.