Dickin' around, no matter when, why or how, can be fun for anyone who enjoys said inane herpaderp in general. It's the same reason why intentionally sandbagging for teh lulz. An example would be how certain Wiichat GE player might do nothin' but run around and throw smoke grenades while cackling somethin' fierce.
Some players do it solely t' gang up on foes as well. The definition of cowardly, indeed. That's how taunt parties evolved from doin' nothin' but taunting and not fightin' back, to ganging up on the opposition in an attempt to win unfairly without tire 'till the others ragequit.