I think Tomte is referencing that it is illegal (and dangerous see guy who died when auto-pilot drove into the back of a truck) to let the autopilot drive unassisted, for example reading a book or falling asleep.
I got the impression though that OP was stating that they used theirs as a "second pair of eyes" and added safety device when they do things in the car that require their hands and attention. This, to me, is perfectly fine. I know people who get around this in normal cars by driving with the knees, or just taking their eyes off the road for "just a second". Using autopilot has got to be safer than that.
I once had a wasp fly right into my face when I was driving, auto pilot would have been great, luckily I was on an empty road, but if I was unlucky enough to need to react fast as that happened I doubt I would have been able to.
the Autopilot can't handle certain kinds of situations, and some of them might appear without much warning. One example from accidents that made the news are stationary obstacles like a police car on the side of the road, but still partly on the road. The Autopilot will happily drive into that obstacle without braking. If there is another car in front of you, this might not be visible until you're pretty close. Taking your eyes off the road for a bit might be enough to miss this.
You can't rely on the Autopilot to prevent accidents, it's simply not designed for this. So you have to pay the same amount of attention as if you were driving entirely manually. So if you're doing stuff that would be impossible while driving yourself, you're almost certainly not paying enough attention to the road and are at least negligent. Not sure about US laws, but usually there are laws against driving in a reckless or dangerous fashion, that can catch all kinds of behaviour.
You're not supposed to be using the "autopilot" as an autopilot.
You need to be always focused on the road and ready to take the wheel at any moment -- which in practice means you can't be using it at all, since "at any moment" means that 2-3 seconds can be all it takes between crashing and recovering from an autopilot error.
I may have worded my reply too strongly, see another comment about "second set of eyes".
But this is dangerous. When I open a bottle in my car, I know that it's a more dangerous situation than usual, I pay more attention, choose the right moment and see that I finish drinking quickly.
A Tesla driver can easily fool himself into "everything's fine, let me sip from the bottle for sevetal minutes and maybe search through my audio CDs".
I got the impression though that OP was stating that they used theirs as a "second pair of eyes" and added safety device when they do things in the car that require their hands and attention. This, to me, is perfectly fine. I know people who get around this in normal cars by driving with the knees, or just taking their eyes off the road for "just a second". Using autopilot has got to be safer than that.
I once had a wasp fly right into my face when I was driving, auto pilot would have been great, luckily I was on an empty road, but if I was unlucky enough to need to react fast as that happened I doubt I would have been able to.