But wouldn't the product sell itself if it is good, why is there need for such content
Well, there have been surveys done by various bodies across the world, which indicate that poor communication strategy and marketing accounts for more than 40% of the reasons behind failure of newly emerging companies.
I have paid attention to a marketing component too and I had had only positive prejudices about it. If each developer so qualitatively approached a question of advertizing, then his project rose by tops much quicker more likely.