It becomes an issue if you're not a sloppy kind of designer/programmer, who just lets the widget flow to occupy more available space. So it's sloppy

It becomes an issue if you're not a sloppy kind of designer/programmer, who just lets the widget flow to occupy more available space. So it's sloppy to build your UI in the exact way it was intended to be built? Not hard-coding every widget sizes is somehow... sloppy? Because the impression I get is that if you can make your app handle different screen sizes appropriately without having to meticulously hand code for every resolution, you're coming out way ahead of the game. That way you present a nice, consistent UX across all devices, and don't have to scramble every time a new resolution or device size comes out. It's also possible to do this with custom interfaces - a little extra attention to your layout engine will net huge benefits in terms of time saved in designing layouts for each of the possible resolutions. Hardware variations, vendor customizations, capabilities variance - these are real issues. Building a UI that flows well across most resolutions and sizes? Not so much. [edit for grammar]