You can have a touchscreen but not actually use it. I have a touchscreen laptop that I only use the touchscreen on when traveling, which isn't that often any more. I forget that it is a touchscreen most of the time, as I've got it set up in stand and the laptop display functions more like a secondary display.

Also, not sure if my own device is just special, but my laptop touchscreen never really shows fingerprints after being touched (while my stationary monitor definitely does if it's touched). It's not the same type of screen as phones and tablets have. (I am CONSTANTLY wiping down my tablet and phone because the fingerprints irk the shit out of me.)

It's not like the device having a touchscreen suddenly means you can't use the mouse and keyboard to do things - the touchscreen is just one of the options when it's there.

Windows has the option to disable the touchscreen as well if it's troublesome, and I would assume Apple would build the same option. (Might not be fair to assume, as Apple does make some weird decisions sometimes, but still.)