Smartphones are designed for men.
I’m not sure that I necessarily agree with all of this, in that I haven’t studied the demographic data in detail, but it seems to make some assumptions about the gendering of hand sizes that seem more “conventional wisdom” than empirical fact (says she with the hands as big as or larger than most of her male friends, thanks to some pretty long fingers).
On the other hand, I remember when the iPhone 5 came out with its bigger screen, and suddenly I couldn’t use a whole bunch of apps properly because conventional UI design was to include things like “back” buttons in the top corners, which I could no longer reach one-handed without shifting my grip (deadly on the cross-trainer at the gym, let me tell you).
On the other other hand, most of the design-savvy apps have been moving their control UI around so that this is no longer a problem (Reeder being one where I’ve heavily noticed the change). So there’s that, too.