Pinning Notifications?

[Fester Bestertester]

This may be older than 15.04: Why do notifications have 'Pin" icon? There may be a reason, but I can't fathom the utility of this, and it confused me for quite a while . Also, why top-right? This is the usual location for a "Close" button. Notifications are easily dismissed by click on Desktop. I'm used to seeing a "Pin" icon, but top-left, in Firefox, in the Newtab page's thumbnails.
Scratches head...

[jlittle]

Just speculating... "Notice boards" were once quite common, made with a panel of cork tiles, that had notices pinned to it with actual pins.

[Fester Bestertester]

Just speculating... "Notice boards" were once quite common, made with a panel of cork tiles, that had notices pinned to it with actual pins.

Yep - and the tradition continues today, public and domestic - the inspiration for the icon. What I'm getting at here is - what is its function here?

[ronw]

I've never had the desire to pin a notification. I often pin the calender, and sometimes the network.

Maybe there are some notifications it would be helpful to keep on screen. Or notifications just inherited the pin from the widget tooltips.