Why Do Physics Joints Always Stretch!?

I have been messing around with Physics and specifically joints for a while now and there is one thing that I cannot seam to fix... stretching joints. You can put two objects with rigidbodies and colliders together in space at identical coordinates and when they hit something the joints stretch apart and spring back together.

I know I could set a low break point but these are not big impacts in the grand scheme of things. The completely separated joint in the last image below is from a...

Why Do Physics Joints Always Stretch!?