Because the House is supposed to represent the district. Prop Rep at the state level, maybe, at most. But I still favour local representation.Well, why have districts when you can have one?
What you're saying for the Presidency, why not for the House too? Everyone votes, count up the votes and hand out seats based on the number of votes?
FPTP leads to the two main parties getting an unfair advantage, which isn't democratic at all.