In the popular way of thinking, people are characterized as if a scale of preferences is hardwired in their heads.
Regardless of anything else, this scale remains the same all the time. This thinking does not characterize human beings but robots. The humanoid robot chooses goods because the valuation scale has told him to. The valuation scale somehow knows which good offers the best utility without letting us know how it knows that.
If the valuation scale is part of the human mind, then it makes a lot of sense to attempt to extract this scale by means of either questionnaires or various psychological tests and laboratory experiments. Once the valuation scale is extracted, social scientists can establish how to allocate scarce resources in the most efficient way.