From what i have heard, fishing can be very time consuming. But if you can get some of the good spells for it, it can be quite rewarding in worlds such as avalon and khrysalis. I personally have not invested my time in it because I focus more of my time on getting gear drops from certain bosses.
You forgot a couple of reasons. If you want to craft mega snacks for your pet, there are recipes for some mega snacks that require fish as reagents. If you are into house decorating, you might want fishtanks displaying your fish in your house. Sometimes, fishtanks can be caught while fishing, along with other surprise drops like pets and things to wear.