I just converted back to homemade from "professional" rubs.
Mostly, it was expense for me. Trying some of the most popular rubs I heard about here (thanks Brethren!), I finally decided that although most of the rubs were really great, it wasn't something that I couldn't do myself. A few of the rubs I tasted, and without a doubt, knew I could do better.
The majority of rubs are salt/sugar, with everyone's standby spices added. That's not expensive stuff, which opens up your wallet to more exotic flavors, like chipotle powder, fancy sugars, powdered habeneros, etc, etc.
Commercial rubs aren't all bad of course. There's something to be said for consistency, and who doesn't love saving time? Still, the past year has taught me it's not the road I wanna travel.
D