Install for Security Fixes
The watchOS 6.2 update includes a collection of security fixes and upgrades. While you may not worry about your Apple Watch security as much as your iPhone or iPad, it is connected and it also stores a lot of personal information.
With each update, Apple adds security fixes. Some of these are named and outlined, which you can see listed on the Apple Security page. Others are simply fixed and may be noted as fixed without further details.
If you've held off on some of the recent watchOS 5 updates, they will be included in this watchOS 6 update to enhance your security and privacy.