Because you cannot have a core that is not part of the class. Therefore, a class must exist in order to have a valid program.
But this is really nit-picking, because in fact you do not need to instantiate this class to do something. You can write a complete program using only static methods that do not create any objects at all.
Whether this is a useful program without using objects such as System.outis another matter.
OO , Java OO, , , ( ). .