You can never "run out of shares". It's just an arbitrary decision to float a number of shares publicly that can be increased or decreased at any time.
I liked your post for one simple reason. You recognize something in me, which you should recognize in yourself. I have very little experience compared to you in the markets. I have been trading futures for 6 years. That's it. You have been trading for many decades. So by default, you have seen what can happen when you mortgage your house to ride a gravy train at just the wrong time. The train crashes into the mountain, and you lose not just your home, but the loan you took on your home to ride said crazy-train. Now yer in a world of financial shit. That is not a place anyone would want to be in, right? So why do it now, as we seem to be in "bubble territory", again?
that's a moot point.... the bottom line is we are running out of 'ownership of profit yielding assets'.