I agree on lane assist, but I'm confused, how does cruise control fail?

I just set it to a speed on the highway... and the speed stays there until I brake.

Are you talking about adaptive cruise control (ACC) to follow the speed of the car in front?

I also don't use cruise control. Not because I don't trust it, but I don't trust myself to react as quickly with it on. If my "gas foot" rests, it will take longer for it to hit the brake if needed, than if I engage continuously while driving. No scientific proof for this, except my own perception of my own attention.

That's really interesting.

Funny, I don't feel the same -- my foot rests below the brake (on the floor) instead of on the gas pedal so the time to move it to the brake feels roughly the same, and I'm paying 100% attention while driving since I'm still steering and constantly monitoring distance to the cars in front of me. So I don't notice any less attention -- it's just a rest for the muscles in my right foot.

But really I'd definitely go with your own perception here -- if you feel like you're paying less attention then it's a good thing you're not using it! Everyone's attention habits and patterns are different. And I'm glad to know people vary in this.

When I have tried to find a place for my foot when driving cruise control, it has happened that I got the toes of my foot stuck under the brake pedal. It was like I was resting the foot partly below it so when I moved it up, it was in the way. Can differ between cars surely. But in the cars I have driven with cruise control, I have not found a comfortable and at the same time "alert" location to put my foot.

I have the same worry when using cruise control. What I've trained myself to do is to cover the accelerator pedal when overtaking other cars or in any situation where I might have to brake. That way the car is still maintaining speed for me but I'm ready to intervene, to get back the safety margin. With adaptive cruise it may even increase the safety as both me and the cruise control can both brake.

Nitpick: 99.(many 9s)% of the time.

I had the power steering drop out going into a turn (fuel pump failure IIRC), and it could have easily caused an accident (I physically couldn't turn the wheel enough to complete the turn).

If power steering fails in speed, it doesn't really matter - the power steering does very little when the car has some velocity. If you can't turn the wheel at speed, then there's something else than power steering pump failing (the steering must have been locked by something else).

Or you have very serious muscle weakness, at which point I'm not sure if driving a car is a smart option in any case.

I expect the total force required to turn depends also on the vehicle's weight, degree of turn, etc. My manual, 90's Japanese sedan (approximately 3,000 lbs iirc) stalled on me while I was exiting a freeway at ~30mph, along a round, ~270° turn. My first instinct was to try put the car back into gear, but before I could effectively do that, I realized I needed both hands on the wheel just to wrestle the car through the turn. I could have easily caused an accident. The disorientation of losing power steering while turning, and having to move my right hand from shifter to wheel made this a serious situation. If my car were heavier, or the turn were tighter, or if I reacted slower, (all of which are more likely than a very serious muscle weakness), it could have been much worse.