Every time I have used a published adventure, I've been disappointed in the quality of the resulting game sessions. My players never do what the adventure expects them to, so I either have to railroad them, or make something up on the fly. I won't railroad, so I punt. But since it's not my material, I don't punt very well.
If I've made up the adventure on my own, then it doesn't matter what the players choose to do, because I know the material inside and out, and I can easily adjust. So from now on, I'll just do it myself. That doesn't mean I won't lift the odd encounter, NPC or map from a published product, but for the most part, everything needs to come from my head.
Here's the thing. I and all of my players lead extremely busy lives. It's sometimes a major deal for us to come up with regular times to play. After we all go to that trouble, why would I want to provide anything less than the best gaming experience possible? Other people might be able to do that with published adventures, but sadly, it doesn't work that way for me.