For me the mental leap was that when I call a function, what I'm saying is "do this, then come back to me so I can finish." What if I don't care if the function comes back, because I've already done all the work I need to do? What if I'm really just handing off my results to the function for it to finish the job itself? Then I should give the function the address of whoever called me, and leave. The function I'm calling is replacing me, not assisting me. If a call stack is a series of waypoints that have to be revisited in reverse after a goal is achieved, with a tail call I'm saying "don't bother coming back to me."

I might leave my house, go to an ATM, then go to the grocery store to do my shopping. TCO means that I don't have to stop by the ATM again on the way home.

So my mental model actually doesn't have anything to do with recursion.