It's a competitive world. There are 10 businesses in your town offering the same thing as you do, marketing in the same way, targeting the same customers.
That's why every detail of your campaign has to be right -- you've got to get the right "message to market match", as they say.
This is particularly important if you are personalizing your messages.
Take a look at the post Let's get really personal from the Marketing Minute blog. It gives a great example of how a marketing campaign could fail because one little detail is wrong.