Goblins are among the earliest evolved sentient life forms of Generica. Rising out of the primordial sludge far before humans or even the faefolk, the goblins took their first steps on land epochs ago while the earth was still tidying up and making a hospitable atmosphere. A cursory glance at one might suggest that although they won the "50 yard dash" of evolution they certainly did not stick it out to win the marathon. You would be partially correct...
The goblin species simply cannot make up it's mind. For the past 700 million years they have been evolving back and forth, in and out of the water. Sometimes regressing to sealife, then getting motivated to join the sophisticated new races on land, only to be frustrated by how behind the times they are. This will cause a species wide depression that sends them again to the ocean for 100 million years or so, with not much to show for their efforts.
The Goblin's of Pageboy's era are once again interested in becoming terrestrial. The shipping industry, particularly piracy, appeals to their sense of mystery and wonder. Since they have a 3 hour memory span, almost anything adds to their sense of mystery and wonder. It also suits them to be aboard boats as they cannot wander away from water for long without moistening their skin.
Goblins are free from any type of reason or morality, simply doing whatever strikes them at the moment. This, coupled with the fact that they are dumber than a bag of clams makes them excellent pirates.