USB port is invariably at the center of the bottom side, there's no industry standard but it's a popular convention. Which means it's inconvenient to hold a charging phone with either right or left hand.

This I actually don't agree with. I don't often charge my phone when i also need it (usually I'm sleeping when it charges), but on the rare occasion that i do, it's not in the way and I can't really see why it would be? How are you holding your phone since it's inconvenient? Standing in your palm??