Because it’s widely considered “throwing your vote away”, people don’t do it, and it never happens. Plus I believe since the president is voted for as an individual, then it’s first past the post. You can’t have a coalition president. The whole system is setup to create a false dichotomy.

Wait till you hear about the enormous number of people that don’t vote at all. I believe if “nobody” was an option, and the non-voters were considered, then nobody would’ve won at all in the last couple of elections. People know the system doesn’t care about them. It’s functionally not a democracy.