Why do all diet ads look like diet ads? For the same reason that all movie ads look like movie ads. And car ads look like car ads. They're slaves to "category culture." It seems that every category has one, and it happens for several reasons:

1) Mis-use of research -- Often, competitors within a category do similar research and interpret the results the same narrow way. Which justifies the same narrow creative solution. A fresh look at the problem will bring new and better ideas.

2) "But we've always done it this way." -- This is the way it's been done in this category for the last 180 years, so it must be right. WRONG, the world has changed!

3) Blind emulation --"Well, the big guy in our category does his ads this way, and if it's good enough for him, it's good enough for us." The way you are marketing should not be the same as anyone or you will not be unique in your clients minds.

So if you are stuck in a category rut, it's time to start a "Cultural Revolution." Throw out the book...and the culture...and rewrite the rules. Because the worst thing you can do when everyone is doing the same thing....is the same thing.