What the author is pointing out is how the social perspective is completely arbitrary, even when it tracks the economic value. Of course lobster will be cheaper / less valuable where it is more plentiful, but it was also viewed as intrinsically worse than other foods, in stark contrast to its popularity today.

What the author fails to point out is that eating seafood every day sucks. It's too rich/sweet/salty. It's like eating cake for every meal. It's not that people are fickle or stupid or whatever he's trying to point out here. No one wants to eat lobster every day. Not even people in the midwest. Ohh, and to add to that, eating a lot of shellfish can cause you to become allergic to it.

Source: I come from a coastal town and love crab, but couldn't eat it more than one or two times a week.

Fish is too rich? I thought that the consensus was that it is appealing because it is a lighter and healthier alternative to meats such as beef, chicken and pork.

Many fish are. Shellfish even more so. Nobody who can help it relies entirely on seafood. Where I'm from, it was the poor children of fishermen who were stuck eating seafood every single day.

The article was about shellfish. I'm sure most people wouldn't have an issue with fish.