It’s also land.
One of the fundamental definitions of a country is borders. A country is a region of earth, and the people who live there and are able to enforce sovereignty over that piece of land.
The electoral college helps us to think not just about the people in America (though those are most important) but also the land in America. If not for the electoral college, presidential candidates would pay zero attention to places like Wyoming and North Dakota. They pay precious little as it is. But those places matter, because they are part of the territory that makes up the United States. Most of the weight will be on those states that are most heavily populated, but the more sparsely populated places matter too, and the people who live in those places, who work in those places and who develop those places should have some say in the government of the country.
The electoral college, by giving a little bit of a boost to states that are less populated, helps hold together not just a bare majority of the country, but also the various territories that make up the country. It has worked well for centuries. And for that reason it deserves to be preserved.