Nintendo Switch Joy-Con Lights Up

I've noticed that after connecting my Nintendo Switch Joy Cons to my computer, the small gray ring around the home button starts to light up. I looked around the settings of my Nintendo Switch, and found that in the 'Notifications' Section, you can find a spot that says 'Notification LED and Vibration'. I'm assuming that LED refers to the LED light on my right joycon. My question is, why haven't I ever seen this before, and what is the main use of it? I'm assuming that Nintendo can light it up when there is a new update for the Switch, but are there any other uses (and is my prediction correct?)

I have just found this about the joycon light :-

Tue 10th Sep 2019 On your right-hand Joy-Con and your Pro Controller, you'll notice that the HOME button has a ring around the edge. As you may or may not already be aware, that ring is actually an LED light; we've seen it light up before but only when a Pro Controller connects to Steam.

Starting from today, thanks to a Switch system update which takes the console's firmware to Version 9.0, the light will finally be used for "alarm notifications". You can see how that works below:

Alarm Notifications have been added to System Settings > Notifications.

• You can check or delete pre-set alarms.
• Alarms can be set up only within supported software (to be added at a later time).
• A controller firmware update may be required to use this feature.

So yes, you are correct with your prediction. As for any other uses I am unable to find anything other than the Alarm notification and Pro control connecting to steam.