There does seem to be a new dynamic going on when it comes to printing because these days many advanced amateurs and pros are printing with prosumer or pro printers. Those printers do not necessarily match the conventional paper sizes (8x10, 11x14, 16x20 etc) that traditional photographers used in the darkroom before digital took over.

That plus that it's so easy to make an image any size you want gives photographers the easy leeway to do whatever they want.

If you are selling prints for a living though - it probably makes the most sense to print them so that they fit into standard sized frames.