As soon as I hit 60, which seems like forever ago now, I was a raiding resto druid. Raiding was fun, and the people were great. The only problem was I couldn't do anything else.
I hated the idea of respecing every day or two so that I could farm the things I needed to keep raiding (namely, pots and gold). This was before healing gear had some damage on it, and before Feral/Balance were acceptable DPS, even when they were the base of your talent spec.
So, I started fishing. It was the one thing I could do by myself that even possibly could make money. According to fishing buddy, I'd fished thousands of Darkclaw Lobster before giving Azshara a rest. This was back when the cast time was 30 sec, and you didn't always catch a fish. I was also lucky enough to have caught a 103 Pound Mightfish, which I think is exceptionally rare these days.
I realized that I could finally "win" something at WoW. I could have the best possible fishing gear in the game, which was all attainable solo as a restoration druid. So I went after the fishing contest, and didn't stop until I had everything.
I was known as the fisherwoman in my guild. I brought fish to pass out to every major boss fight (which was, at the time, primarily Ragnaros). I had installed an addon simply for the purpose of splitting stacks of fish into pairs and trading them based on what class opened a trade window.
I wrote up a guide to fishing, and particularly winning the fishing contest, since I was frequently asked questions and advice. So, when the expansion beta rolled around, I submitted the fishing contest guide to some website and won a beta key. It was then that I found El's site, which had more patch 2.0 fishing information than I could have ever compiled on my own.
Sorry... this is getting pretty "TLDR." I'll sum up by saying, I started fishing because it was the one thing I could do alone, being resto spec'd. I kept fishing because it was relaxing/fun, able to be "won," and it's good money.