Allocated based on population would mean that one vote in one region should be equal in weight to one vote in another region.
Granted that no system can be perfect and actual voters are not equal to population of course.
Hey, maybe one man = one vote is a bit cliche, but your side has used "if it ain't broke don't fix it"
So what is broke about it?
In the constitional convention where the constitution was written the big states like New York wanted one man one vote but the more rural states would refus to join the club under cicumstances that ensured that practicly all decisions to be made in New York City , simularly Southern states wanted indians and slaves to be counted in the census but northern states objected that this wouldn't be fair since these people were not allowed to vote.
I don't know why Rode Island would ever join a club in which it had no influence , or why New Hampshire should have to put up wih a Slaves ficticious right to vote carrying representation in congress.
So to get the club together comprmises were made. The contract got signed .