My reason: North American native fishes have the American eel, a REAL eel that can tolerate freshwater, not some fake eel like spiny eels.
American Eels can tolerate almost anything. Have you ever seen them attack crayfish? Mine decided he was going to eat the biggest crayfish I have. He snatched him up and proceeded to the corner of the tank to death-spiral him until his claws flew off. It was CRAZY.
Back on topic:
Why? Interest. They aren't captive bred, they aren't farmed, and they aren't colorful decorations to impress visitors. OR: Some jerk in a store doesn't determine how much you will pay him because he had to have this poor fish shipped 1500 miles in a rubbermaid tub to be put in a substandard environment and oogled over. Very similar to animals. Anyone can go to a petstore and buy a sugarglider and be 'cool'. But to me an Alligator Snapper or common Crow are far more interesting.
I'm not attacking anyone either - just my feelings. All my fish are rescues (nephews net, dog, etc.) with the exception of crayfish. I keep them to clean up the bottom of the tank. They eat everything. Although (strangely enough) their favorite food is Krill. Odd, I know.