One Fish...Why?

I understand dogs, and even cats to an extreme, even though they are vicious pieces of shit half the time. Fish however make no sense. You can't pet a fish, well I suppose you can if you want to walk around smelling like sour pussy all day. An aquatic pet won't hang out in your lap without dying, or play fetch. So what's the point? The only exception are the big fat fish that can live through eating a piece of pizza and sharks. The only entertainment value you can get from anything else is watching it take a shit.