Why do we only eat the adductor muscle in scallops but the entire visceral mass of other bivalves?

I just dont get it. Ive never eaten any other part of a scallop aside from that one muscle. It just seems like a huge waste of meat. As you can see that muscle really doesnt take up a lot of the scallops mass. So there is still plenty of other meat. Does the rest taste really bad or something?

Another thing is you next to never see scallops served in the shell which I find pretty confusing since their shells look pretty. Much cooler than a boring clam shell or ugly oyster. Any reason for this?