Drawing annotations is another. For example Slack screen share, whiteboard apps, and so on.
Of course there is the touchpad, but in these cases - especially when we are looking at something together - the touch screen makes more sense as an interface.
Gestures on the screen also tend to be 1:1 so there's more precision for these types of gestures.
I could see how touch screens would benefit those with a11y issues. We already know mouse control is an issue for many.
They do many manual things, comparing lists and whatnot (yeah, I know) and they absolutely love being able to directly click things, or scrolling the contents on one side without moving the mouse pointer from the other.
I think the point is that this opens new avenues of interaction with the machine. Of course, there is the risk that things would get overly adapted to touch interactions (even more white space, giant buttons, etc), which I'd hate.
Currently using a Wacom One w/ my MacBook 13" as a 3rd display (in addition to a 4K 27") and the stylus is quite nice (bonus that it's the same as for my phone (Galaxy Note 10+) and e-book reader (Kindle Scribe) and it's quite nice to be able to draw/annotate at will --- missing Calligrapher, née Rosetta, which was the handwriting recognition from the Newton MessagePad.
Apple is just going to look ever more out-of-synch as touch becomes ubiquitous, and less innovative as designs such as Lenovo's dual-screen Yogabook 9i reach the market. Once upon a time, the Compaq TC-1000 was described as a product which Apple would make -- what could Apple do in this design space?
Is forcing the user to have a second device for touch, and then not allowing touch to function fully when using Sidecar a valid approach in the marketplace?
If Apple would do a dual-screen device like to the Yogabook 9i which supported the Apple Pencil, and made an iPhone which did as well, I'd sell all of my current devices (except for the Kindle Scribe) and buy in to it.
If you observer people who use a touch-enabled laptop, they will dynamically switch interaction modes depending on the situation. Scrolling the screen, pressing a button, dragging an element, zooming are all actions that lend themselves to touch. It is not an either/or choice. That is why fears of “gorilla arm” are overblown. I also find that switching modes can be a relief when the keyboard or trackpad/mouse gets tiring. It helps to switch up movements to avoid repetitive stress.
my thinkpad (t25) has a touchscreen, of which I am occasionally reminded of by accidentally brushing the screen with a hand. Really have no use for it and don't want to be touching a screen in the first place. It's like putting fingers on your glasses.
Touching objects and performing gestures on the screen is much faster than having to move cursor around with TouchPad and click things.