In what way is fishing better than crabbing?

Excuse my idiocy if there is something I am not understanding. Anyway, I have done both fishing and crabbing and strangely I've been able to catch a much bigger variety of sea creatures by crabbing. Since crabbing usually consists of a cage or a bucket or a net (which means people can catch bigger animals with a bit more ease)...why do fishermen fish? Is it just for sport or is there something more beneficial to it?