It's only in the CC version of Lightroom. It may be added to LR 7. There are a few threads about this if you want to have a look.
This makes no sense - Lightroom 6 has not been out that long - if it is such a great feature why was it not included with the upgrade or is it Adobe's policy to do frequent version upgrades adding just a few features each time in order to squeeze as much money as possible out of their customers who choose to work without relying on internet access. Looks like Adobe has taken a page out of the Microsoft "playbook" - that is why I am now an Apple owner. Guess I will be starting to look for a standalone replacement for Lightroom that does not withhold a feature from one segment of their customers.
And why not Creative Cloud - it provides way more than I need - I have absolutely no interest in Photoshop - and the least expensive plan still has that included. Why should I pay for something that is of no interest to me? Also I frequently work on planes and trains without internet connection or in locations with poor bandwidth so I need standalone products that do not rely on having internet access to work.
It makes perfect sense. You purchased Lightroom 6, and the feature set that was available when Lightroom 6 was offered. Lightroom CC is going to receive more frequent updates and new features that Lightroom 6 will not receive until such time as Lightroom 7 is released. You cannot purchase a standalone version and expect to receive all the benefits that CC subscribers receive. It was clearly stated that the Lightroom 6 feature set would not be updated. Lightroom 6 will receive updates to support new cameras, but will not receive the new features that Lightroom CC receives.
As far as the Internet connection is concerned, Lightroom CC only has to connect periodically in order to verify that your account is paid current. That is about once a month if you are paying by the month. Otherwise, Lightroom CC can run without an Internet connection.