To understand it, you must first understand the original intent. Originally, there weren’t really parties. People voted on local representatives that then all got together, debated, and decided on a president. So you voted on a representative in the debate and ultimate election process. The idea is that people in the states know their local representatives better and can trust more in electing an educated knowledgeable person with similar local interests to represent them in that actual election of a president. That’s why it’s there and why it started, though in the modern day bastardized version, it no longer serves that purpose.
It also, because senate seats are not weighted by population, slightly increases the say of people in smaller states helping to prevent small rural areas from being trampled by larger denser population centers who have vastly different interests. It does still serve this purpose.