"You find two-stroke engines in poorer countries because they're cheap,"
No, you find two-stroke engines in applications where you need high power but extremely low weight. Their cheapness is simply a byproduct of their simplicity (hence, weight savings). There are plenty of applications where a 4-stroke engine simply wouldn't work because it would weigh too much (leaf blowers, chain saws, etc) or would be too bulky (mopeds, model airplanes, lawnmowers, etc). Sure their efficiency needs some work, or replacement if a viable alternative is created, but at the moment there are several applications where 4-stroke engines or battery power simply wouldn't work.