I think one reason could be: how would it handle the folders docked on the right hand side of the Dock? Currently when you click them, they generate a pop up list, stack, or grid that you need to then use the mouse or pointer to select...
A similar process initiated from the touchbar would necessitate a touch screen...
Apple does not approve of games running on the MacBook Pro's Touch Bar, based on its strict Developer Guidelines. According to Apple, the Touch Bar should be used as an extension of the keyboard and trackpad, delivering contextual controls for apps, instead of as a display.
For the love of God, please don't ever let Apple control what you can put on a Mac, they should NEVER wield that power.
As for the touchbar. As much as a crap time I have been giving Apple on here, I actually think the touch bar is neat and has utility (only spent a little time with it in store).
I do understand its not for everyone e.g. especially the cost that it adds.
The touch bar could display one massive battery life indicator...
...or maybe a dongle counter? Attach as many dongles as you can to hit the red region on the far right of the display for extra points!
Just reinforces the notion of how gimicky this is. I'm sure there can be fair amount of good uses for the TB, but when we see these fluff type applications I do wonder.