The other is your hand would occlude what you wanted to see, and the third, which was the winner, was that your fingers would get the screen dirty, and hence, fingers would never be a device that you'd use.
Outra é que sua mão obstruiria o que você queria ver, e a terceira e campeã é que os dedos sujariam a tela, portanto os dedos nunca seriam um dispositivo que você usaria.