Marketing is not just about growing. It is also about choice. Sure you want to give your customers choices, but you also want to be able to choose your customers. If you have a steady flow of inquiries and leads, you have more control over the kind of business you take. This is especially true for B2B companies, but it also applies to B2C. Retail and consumer marketers discriminate with price and distribution. Business to business marketers can discriminate with price, type of project, and by sometimes just saying, "No, we don't think this would be a good fit."
You can only say "no," though, when you have options, and the best way to have options is by keeping your message in front of your customers and prospects. This is why the best companies never let their foot off the gas of their marketing or their innovation. Innovation gives you a reason to market and a message that connects. Marketing that innovation communicates value and distinction. When you have that, you can say "yes" to the customers and business that you really want and "no" to the business that isn't profitable or otherwise doesn't fit.