Hi Selina, thanks for reaching out! 

In general, this is simply how pinning tabs work for most products. 

To "pin" a tab in a web browser for example allows you to keep a specific website tab permanently open and easily accessible. For example using Google Chrome, pinning a tab will pin to the left side of the browser window, even after closing and reopening the browser. Pinned tabs are smaller than normal tabs, and will showing only the site's icon and not the title. They are also designed this way to prevent accidental closure, since they will lack a close button.

Hope this helps explain!