You remember that 250MP prototype Camera from Canon? On that video you can see why the hell that crazy Megapixel number matters! The tester sent me (And Also CanonWatch) that text:
The test with the 800mm lens is impressive!
A advertising on an hotel can read with the 800mm on top from 15km distance!
An human can see from 3km distance.
A big building can see from a distance 20-25 km with a normal lens!
And canon can stabilize the ,,fata morgana effect” (see at 2:04 min) from hot rising air. Canon call it ,,removal Turbulence”.