It wasn't for removing the clutch and pressure plate as much as it was for being able to remove the flywheel without having to drop the complete oil pan.
In many c&pp replacements, with a one piece oil pan, folks chose not to have the flywheel ground because they did not want to go through the hassle of removing the oil pan with the engine in place, and they definitely did not want to remove the complete engine to take the oil pan off. This resulted in many new c&pp replacements be done half a$$.