I like to read about the different species, but I have two big caveats that keep me from purchasing any.
One is that I don't trust myself to care for them properly. I'm really not that good at this. In fact, if you ask me, I'm downright terrible. I don't even know what I'm doing wrong, that's how bad it is. I'm not going to buy fish and watch them die. It's cruel, and besides it's a waste of money.
Also, I'm really hesitant to buy wild caught fish. I'm not convinced that fish raised in large farms is better - I don't like either option, so I'm stuck not knowing where I would feel comfortable purchasing any fish. On the non-aquatic side, I heavily advocate adoption of animals. There isn't really an equivalent for fish/aquatic invertebrates.