Maybe not any car but I guess you've never jacked up this car and understand the dynamics of it. If I were to remove that floor jack from the rear all together, the back end of the car might drop only 4-5 inches due to the stiffness of the chassis. How do I know? I've done it. But like you said, you wouldn't get under it, but I would and have and will continue to do so because I know that even if the jack failed, the car won't go anywhere in that configuration.
I had another owner over here yesterday for some "undercar" work. I jacked it up similarly to what you see in this picture. He was like because he had never seen his car jacked up at such an angle. It's all what you're used to.
I know you'll have to try it before you believe it but, you can jack up the car like this ANYWHERE along its side and the whole side will come up. Similarly, you can put a jack stand under ANYWHERE along its side and it will hold the whole side up (as long as the other side is on the ground).