Hmmm...
Heh, I can see where you're going with these. It's nice thinking, but it's missing something.
Have you held a piece of stranded wire in your life? How the heck are you going to coax every single strand into a just-perfectly-sized space? (If you have a solution for that, I would honestly like to see it. Every so often I find myself wrestling very fine strands (might be welding cable, might be litz cable) into a crimp lug. Such a PITA when they're tight fitting!)
Even if it's solid core wire, how are you going to have adequate retention force, while also being able to push the thing in?
For the phono jack: how are you going to insert the wires, or tension the springs, while also stretching the spring over the connector body?
For the square pin connector: the square pin spreads the terminal frame apart, loosening the wire, doesn't it?
Tim