Greece have had easier qualifying groups for major tournaments relative to a team of their ability level thanks to their greater status following Euro 2004. They've never had to contend with any of the 'big' European teams - France, Germany, Italy, the Netherlands, England, Spain etc. - in their group.
I could understand if they were so unadventurous if they were playing Brazil or Argentina, but they are in a relatively weak group consisting of Colombia, Ivory Coast and Japan, teams they are more than capable of beating.
Why go to a World Cup just to make up the numbers?