Each state is a constituency for the senate - it has two senators to represent it.
Each district is a constituency for congress - it has one congressman to represent it.
Each nation is a constituency for the president - it has one president to represent it.
Every voter within a single constituency should have a vote of equal weight in a representative democracy. This happens for senators and congressmen, but for obsolete historical reasons, does not happen for presidents.
And people who can immediately see the problem with a suggestion that each voter should have their vote weighted by how many kids they have, or how many cars, or how many dollars, or the floor area of their residence, seem for no good reason to think it's OK to let voters in presidential elections have a vote weighted by the population density of the state in which they live.
It's bizarre.