If most people live in the cities, I don't see an argument for letting rural areas have more than their proportional share of representation.
One person, one vote.
Not to mention that the US has a surplus of food, and the US government often pays farmers not to make food, so their value is really overestimated, if anything, especially considering all the subsidies they get at the expense of more populous states.
Most of the people that work in agriculture are probably undocumented immigrants with zero votes and zero representation, and those people who claim to care about the welfare of agricultural workers should have undocumented immigrant rights and representation at the forefront of their agenda. But somehow anti-immigrant, and thus anti-agricultural worker sentiment is rife among such people.
Many people are still under the illusion that small family farms are the ones that are being supported when they give agricultural subsidies. But those people are mostly gone. What are left in their place are huge corporations, and it's they who are benefiting most from the status quo.
It does act to prevent the rural areas from becoming totally neglected hinterlands, help them implement polices that may be necessary because of the different conditions of non-urban areas.
That said, I do think the current bargain tips the balance too much, so I'm now in favor of abolishing the Electoral College, and giving the House an advise-and-consent role (in addition to that of the Senate), at least for judges. These smaller states can keep their extra representation in the Senate.