I completely agree with that but then the user has the little fold out arms that normally hold the phone, as the area to hold the unit and get that balance. Now... if DJI had mounted the screen above the sticks and assuming , relocated them below the screen, so just the opposite of what they currently have, that would leave nothing below the sticks, to get a grip on, and that would be a terrible design to hold and balance.
To get an idea of that sort of feel, fit a phone in the current controller then rotate it 180 degrees, to have the screen on top, and see how that feels, for all those saying they wish they had mounted the screen above. Don't get me wrong, I too would have liked to see the screen above the sticks, but to get the balance correct and the hold position comfortable for your hands, they would need to have extensions on the main body below the sticks, to get the grip and feel correct on a controller.
This would have made the controller longer still, which would then be a storage problem for everyone. Maybe they could come out with an Ultrabright version with a 1 inch larger screen (or1.5 inch) and then have the screen on top, with fold out arms along the bottom, below the control sticks. Sort of like they have now to hold a phone, but these would just be for giving a comfortable holding position, yet by folding back in, it would reduce the overall size for storage.
They could have mounted the sticks on the side of the screen and upper of middle position for a comfortable hold, but that would make the controller wider, again a storage problem. No easy fix to make it a nice viewing position, balance and size for storage, really.