CORDED: The reason a chain saw can't use a power cord is that it would need to be hundreds upon hundreds of feet long and would be impossible to drag through the chaparral without catching on scores of bushes, rocks, and trees.
CY: Even with a portable generator, still not really convenient.
BATTERY: The reason a chain saw can't use a battery is that it would die after felling only a few trees and cutting up the limbs. We'd spend more time waiting for it to charge than cutting.
CY: Need the new Nuclear Power Batteries. They are sold out of North Korea, on Ebay. Don't want the Iranian Nuclear Power Batteries, they sometimes explode.
FOUR STROKE: The reason most chain saws aren't four strokes, as far as I can tell, is that four strokes without oil pumps can't be placed in all the positions that a chain saw needs to be without spilling oil into the cylinder.
CY: And they are heavier. The used to be made, for felling trees. When one knows the saw operation is always going to be in the same position. They were operated by two men.
TWO STROKE: The reason most chain saws are two strokes, I presume, is that is less expensive than a oil-pump driven four stroke and the two stroke works in any position.
CY: Also, the two stroke fires on every piston stroke, so the HP to weight ratio is much higher.
BTW, if there are good four-stroke chain saws on the market, let me know which you prefer.
CY: I havn't looked, but they are likely out of the home owner price range.