It wasn't until Claptrap's Web Series that it actually developed the passive-aggressive persona that appears in Claptrap's New Robot Revolution and subsequently later games.
They served mainly as a way the characters could access new zones or upgrade their backpacks.
(Claptrap even says it has two robot arms, as a reference to how Gaige has one.)
Eventually Angel suggests that the best way to make Claptrap work as a soldier is to "work with the idiocy, not against it." This is the reason why VAULTHUNTER.EXE is as random and uncontrolled as it is: the aspect of the code that would have made it work properly, known as Shadowtrap, was self-aware and so hostile and malevolent that Claptrap's own security systems automatically quarantined it. When Jack tries to make Claptrap into a viable robot soldier, he gets frustrated and furious because every time he activates it, Claptrap just won't stop dancing.
They're so problematic that Jack ultimately destroys the entire product line because he hates them that much, and due to a bad (and downright surreal) experience with one trying to unlock a door. Afterwards, The Pre-Sequel! reveals that this is because the Hyperion AI researcher who designed them in the first place died before he could fix their programming.Instead, it led the rest of the Claptraps in a ( not entirely unjustified) revolt against the humans. The intro of Claptrap's New Robot Revolution reveals that it was originally sent by Hyperion to kill the Vault Hunters after they became a drain on the economy.Is a Crapshoot: Its entire model line is erratic and unreliable at best.