> someone needs to be getting less for doing more, so that someone else doing less can have more

This is true of all societies, not just socialist ones. In capitalism, it's called philanthropy and charity. The underlying social contract is noblesse oblige, that the right to enjoy the trappings of wealth comes with an obligation to ensure that the poor are reasonably taken care of.

The real difference that socialism poses is not that it should happen at all, but that it should happen by force with the power of the State, due to the wealthy as a class no longer making the independent free choice of discharging such obligations.