Yes, and then people would start loading them _yet_ heavier. If the 450 kg limit is not respected today* why would any other limit be respected tomorrow? It is a general characteristic of (a certain type of) humans, when given a finger, to take an arm.
That's a vicious circle, with no foreseeable end. Increasing the legal limit solves nothing.
*It isn't indeed, by many. Myself take care: I mostly fly alone, and when I take a passenger it will indeed be for a local bimble.