Cec Murphy is running a series on his blog about marketing. Writers need to know how to market their books. It is very important to stay informed on the current trends.
If you don’t study the markets, you lower your chances of selling anything because you don’t know what publishers want. If you send in something that’s outdated or no longer of interest, you frustrate editors. Do it often enough and you create a negative reputation among editors (and they do talk with each other). Learn more.