1.The cost savings is significant.
2.You get it built exactly the way you want it. Thread color, seat style, guide color-type-placement, handle style.
3.Better customer satisfaction. The factory will not take the time to build your rod the way you want it, you buy the rod the way they want to build it!
4.Get your name (or someone else's) built into the rod. Add a message like “Happy Anniversary” or “From Dad”.