Because juries (in some countries, see https://en.m.wikipedia.org/wiki/Juror's_oath ; however, includes France) take an oath to examine the evidence presented and judge impartially to the best of their ability. Voters don’t.
At the presidential level I would say the law should follow the (will of the) people and not the other way around. After all, those irrational voters are the ones who created the law in the first place, in so many ways. As an aside, the more I think about someone being able to truly be impartial, the more I giggle. Myself included, of course.
