They have to because of stupid pinch-to-zoom. You either have to balance the phone in the palm of your non-dominant hand (literally switch the phone from one hand to the other) while pinching with your dominant hand, or do a sort of goatse thing with your thumbs while holding the phone in both hands.
Screw-to-zoom is a million times better: draw a spiral to the right and you get closer, spiral to the left and you get farther away (agreeing with the "righty-tighty, lefty-loosey" standard.) Easily done with any single finger, or even with the thumb of the hand holding the phone (for people with adequate thumb-wrestling skills.)
They have to because of stupid pinch-to-zoom. You either have to balance the phone in the palm of your non-dominant hand (literally switch the phone from one hand to the other) while pinching with your dominant hand, or do a sort of goatse thing with your thumbs while holding the phone in both hands.
Screw-to-zoom is a million times better: draw a spiral to the right and you get closer, spiral to the left and you get farther away (agreeing with the "righty-tighty, lefty-loosey" standard.) Easily done with any single finger, or even with the thumb of the hand holding the phone (for people with adequate thumb-wrestling skills.)