YOU don't see. YOU are used to use both hands. Some of us aren't. Why use 2 hands when only one is needed with an iphone SE ?
I'm gonna ask you then why 99,99% of products designed in the last century were designed for a single hand ? Because there are a lot of scenarios where we require the other hand for other tasks..
That's why i won't buy another iphone if the screen is bigger than iphone SE.
I understand a lot of users use their phones all day long as a computer. Personaly i work all day on a computer, and don't need my phone to do difficult tasks, and so i don't want a phone that REQUIRE me to use both hands.
Bigger screen is a market demand, but also a design issue, they can't fit a lot of technology + good battery life in a small phone. I hope Apple will solve this problem.