They said "I also used to mock them, but then after having PCs with it, I find myself stabbing the screen of my 12" MacBook (the only Apple device I've owned that I've despised) only to have nothing happen." That means they got a laptop that had a touch screen and used it. How much did they use it? So much that they now naturally tap the screen instead of using the cursor, even when they are on a different device.
You are correct that not all professions use it, but I can confirm that the medical, research, and academic fields love it. Maybe the reason most professions don't use it has more to do with slow adoption and not limited need? Having worked at some different jobs I feel comfortable saying that just because something might improve productivity doesn’t mean that an industry will adopt it.
Oh, and the ergonomics argument is hogwash. Touch isn't an exclusive input. That's like saying joysticks are useless because they aren’t good at being a mouse.