Why do Authors massively underestimate the importance of their Book Cover?

It's quite interesting that most authors will spend hours and hours writing out a perfect Book Description, which no one reads (yes, Seth Godin is right - Book Blurbs don't matter at all) And At The Same Time Those same authors will pick out a cover at random, or take 10 minutes on Photoshop to make their cover Your Book Cover is the Single Most Important determinant of Book Sales - It is...