Corner 3s are shorter because the 3-point curve flattens to give enough space to move between it and the bounds. The action in the corner is also less dynamic because it's hard to drive to the basket from there, so either you shoot a 3 or pass to center which resets the play if you can't find someone driving up center court. Here's a diagram of a regulation NBA court showing the issue. https://upload.wikimedia.org/wikipedia/commons/7/7d/Basketba...