I think every fly tier asks him/herself this question at some point or another.

Do I tie becuase its fun?  Do I tie because I like designing my own patterns?  Do I tie for money or commercially?  Do I tie to save money? And the list seems to go on for eternity....

For me, I tie for all these reasons and more (except maybe tying commercially).  Ask any avid fly tier and fisher, and almost all of them will describe to you a feeling like no other when you catch a fish on something you made with your own two hands.

I guess the reason why I really like fly tying because it makes me feel more like I'm  living off the land, and providing for myself.  I mean, it's not like you could just be walking in a forest, see every material you need to make a senko bait, pick it up and then bring home to assemble.  But, on the other hand this is very possible to do by subsituting a simple nymph fly in for the senko.

So, for all those fly fishermen that are not sure about the benefits of fly tying to buying flies, I'll tell you right now a smart decision that you won't regret will be to dive right in and start tying.  Buy a simple vice and beginners tying kit and you'll be "hooked" (sorry for the overused pun) on fly tying.