Literal numbers that are unproportionally skewed by two overpowered population centers. It isn't just about proportionally capturing the interest of the individual voter. That individual voter in each state represents a sum total of different interests than a individual voter in another region of the States.

California and New York have different exports and interests than say, Wisconsin.

You would feel quite different about granting power to overpopulated areas if they were conservative rednecks, wouldn't you? Of course you would.