Look up three posts above that:
I'll give you a clue why I didn't use one....exponential growth is unsustainable, and the barrier to entry is greater with a higher price, even if percentage of growth is the same (which is one reason you see stock splits).
Uh.. that's your explanation?
Stock splits exist because you can't buy half a stock.
And for the exponential growth...
Unsustainable? Perhaps. But until we hit a hard limit, that's pretty much the best way to characterize it.
That's a double exponential, by the way.