I agree with B. Diddy, some apps force a screen orientation. I have several on my tablet (Galaxy Tab S3) that force portrait (Running Circles, Mini golf King, Bejeweled Blitz as examples) or landscape (any of the Angry Birds, Pacman as a couple examples). I have some that support both orientations, one that comes to mind is a Minesweeper (think back to the Windows 95 days), and the board actually adjusts to the orientation change with different best times for each I think since the number of mines to find is different.
These are actually choices by the developer, though not supporting both orientations COULD be seen as laziness on the developer's part some apps are just plain better in one orientation over the other.