Gerrymandering only works if you can group people together, the larger the group the easier it is to disenfranchise them. Less reps means larger groups of people.
Put it this way; a large city of 700k people would be split about 7-8 times where as the smaller cities would be unaffected. That's 6-7 times more the representation it would have. Currently cities are under represented.
In almost all states, if not all, the only people that would actually be represented are those in the cities despite the state being mostly rural. Why would a rep give half a shit about the minority of the population who live in rural areas? Same argument for not using a straight popular vote for President, they already don't give a fuck about half of the states. If it was a straight popular vote they would almost exclusively hit/cater to the uber mega cities and dense population centers.
Congress has tried five different algorithms to tackle the problem since 1789, finally landing on an elegant process called the “equal proportions method,” which has been in use since 1940. The way it works is quite clever. After comping every state one representative, this algorithm uses a round-robin system to apportion the remaining 385 seats one at a time to the state that needs another seat the most, until every seat is assigned and so ends the game of musical chairs. That neediness is calculated by taking each state’s population and dividing it by the square root of the number of seats it has thus far in the process multiplied by that number plus one — which is to say, a weighted prediction of how much better its people-per-representative figure would get if it was awarded the next seat. (This is known as the “geometric mean.”) After each seat is assigned, this neediness is recalculated and usually a different state rises to the top of the priority list.
The method isn’t perfect, but it is the best way to minimize unfairness that lawmakers could agree on 80 years ago. And it’s not a bad solution. The problem isn’t the math. The problem is that there just aren’t enough seats to go around.
So how many seats are ideal? To determine the magic number, I ran an experiment in which, using this official method of apportionment, I calculated how many delegates each state would get for every number of total seats from 435 to 1,305, three times the current figure. For each result, I then computed the disparity in representation using a basic standard deviation divided by the average value — a Stats 101 figure called the “coefficient of variation” that broadly measures how much disparity exists in a set of values.
The results were curious. While the disparity declines as the House gets larger, as one would expect, there are certain key numbers of seats that
Looking under the hood, these magic numbers occur when the last underrepresented small state gets the last available seat. While even adding five seats would slightly improve the House’s fairness, the disparity really starts to drop around 775 seats. Then, interestingly enough, it actually gets worse for obscenely large numbers of representatives. The optimal value, within reason, is 930 seats, which would look like this: