Is there any real need of Marketing skills for Developers?

Normally, developers know the product so well that they could be the best salesman of the product.

As Market pays the money for the product, Market decides the success/failure of the product. So it is very important to know the market.

How product is used in the market?
What are the most popular features?
What are the most useful features?
What are the most useless features?

What are the bugs?
What are the new feature requirements?

Once developers knows these things, they can create better products generating better value for customers.