How so? I can still hold and use the phone exactly as if it had no case including putting it in an, otherwise empty, pocket if I wish with the flap left folded back.
You seem bothered by the fact I don't think I'll be putting a case on my phone. (I still may get one; it just depends on what I think of the phone when I get it.)
Anyway, a case (even a slim one) makes it bigger, bulkier, and hides the lines/aesthetics of the phone as it was designed. It doesn't necessary make it uglier, but it does add to the size and weight, even if just a little. And yes, a phone with a case will still fit in my pocket and I can still hold it normally. Heck, my M8 with it's Spigen slim armor case
and my wallet both fit in the same front pocket of my jeans. But it doesn't look nor feel the same with the case.
My whole point, though, is that the 640 is a pretty inexpensive phone and I can go out and replace it a lot easier if it gets broken than I could a phone that costs $500 (like my M8, which wasn't cheap). Not to mention my phones don't get beat up too much, so it's low risk for
me, although that's not true for everyone.
To each their own. I was throwing out an option to the OP that going without a case (and screen protector which I haven't used in years and never had a scratch) is an alternative.