Advanced driver-assist systems like Tesla Autopilot aim to save lives, and they do, but they're not perfect.
All advanced driver-assist systems save lives. It doesn't matter the name of the technology or the automaker, the goal here is to "assist" drivers. While legacy automakers tend to call such features collision avoidance, automatic emergency braking, and the like, Tesla's suite of features is called Autopilot. In airplanes, Autopilot "assists" the pilot, so it makes sense as long as you don't read into it too much.
Regardless of the above, Autopilot and other driver-assist systems work to assist when a driver doesn't react. However, this doesn't mean you can get drunk, go to sleep, and count on the car to deliver you safely to your destination. There are a number of factors involved, so while the car is "assisting" you, you have to remain aware as well.
There are plenty of videos on the internet showcasing Tesla Autopilot successes and failures. However, we typically have no way of knowing if Autopilot was actually engaged or not. As you can see in this video, the van crosses over the lane line and sideswipes the Model 3, collapsing its side-view mirror and making slight contact with the side of the car. Both vehicles are able to continue driving, but clearly, this is a collision.
The person who posted the video says the Model 3 was on Autopilot and failed to detect and avoid the van. This could certainly be true. At the same time, some people will argue that there's no way Tesla Autopilot was engaged.
In the end, it doesn't matter what the story is. The point here is that even though advanced driver-assist systems save many lives, they're far from perfect. You can't count on them or trust them. All you can do is have peace of mind knowing that if you miss something, there's a good chance the technology will catch it. There's also a chance it won't. Keep your eyes on the road and remain aware at all times, whether or not you have a car with active safety aids and self-driving features.