A lot of anglers use the popular brands of nymphing leaders and they are very successful on them, but for me I like to be a bit more three dimensional with my leader set up. There are several reasons to use made up leaders over the generic leaders you can buy.
I make my own leaders for several reasons to improve this process:I can use formulas to build the leader that suits the way I fish, cast, reach and strike fish.I can put extra spring in the leaders by boiling them to allow me fish lesser diameters with fewer break offs and makes the leader more supple while having better contact with my nymphs. I can again make different leaders up not just for lengths but also some more aggressive and progressive than others to aid my casting in different conditions. I can add in what I call a locator section up the leader firstly to train my eye to find the thin indicator immediately and secondly to allow me to fish different depths as I make my way through the beat, using the locator as the indicator when I move into deeper water. These are all points that I have put in place to make the process of casting and contact much more effective when I am nymphing.