[dahdum]

The real answer is because we’re a union of states, many of which would not have joined under that representation scheme.

You need to amend the constitution to change that. It’s hard to do, but again that was intentional.

[munk-a]

America was originally a union of colonies separated by economic focuses and communication difficulties - those concerns are no longer relevant in the modern world and sticking to a tradition because "that's what it's always been" isn't a good general policy.

[dahdum]

It's not just tradition, it's law written into the kernel of the country. Changing it is possible, it's just not easy, and requires the support of those who would "lose" under the arrangement proposed. Some compromise will have to be made to do so.