I don’t use the Touch Bar as much as I once did (see below), but one usage for me is to answer and end calls. When I’m out of the office I can still make calls, using my office phone number, via our VOIP app on my MacBook. If the receptionist calls me, I used to try to quickly switch to the app, find the “answer” button, and click on it. I’ve now set up a Keyboard Maestro macro, mapped to the Touch Bar via BetterTouchTool, to do that for me. I have another I can tap to end calls.
The lack of a separate keyboard with Touch Bar support has significant reduced my Touch Bar usage on my MacBook. The main usage for me on the MacBook was to address “keyboard shortcut overload.” I would make some buttons so I didn’t have to remember new shortcuts. But since I couldn’t carry that over to the iMac during the day, I stopped using most of them. One example of that is Markdown bold and italics. I had a button that would take selected text and surround it with the correct Markdown syntax. I eventually just forced myself to learn another keyboard shortcut, though, so I could work the same way on my iMac.