Why do photographers need to market themselves? In a phrase: so that you don't starve to death. No, but seriously. Otherwise, you risk ending up like Vincent van Gogh who (in the words of Steven Pressfield) “produced masterpiece after masterpiece and never found a buyer in his whole life.”
Bestselling author and marketing guru Seth Godin published an interesting thought to …
When the web first emerged, web design knowledge was a scarce commodity, and developers were able to charge ridiculous amounts of money to create simple websites. Now that everyone and their mother knows how to do simple HTML, you'll need to learn a lot more and offer something unique to stand a chance in the freelance market.
The exact same thing is happening in the photography industry. As the cost of shooting, printing, and distributing photos goes down, simply knowing how to take "good pictures" is no longer enough.