I agree with everything you just said except this conclusion:

“It’s a useless feature in search of a use-case”

Sometimes it’s going to be easier to pinch to zoom, for example, than do the same thing with a keyboard or mouse.

Touch is no longer an expensive feature to add, so it makes sense to add it for certain use cases.

Also imagine a Mac being used in a kiosk situation where an iPad isn’t big enough.

I wouldn’t be surprised if we eventually get a Mac that is essentially a giant iPad in form factor which can operate in both modes. On a stand to act like a desktop, or on the table, to act as a giant iPad. It would make little sense to disable touch when in upright mode.