Much as Soundwave has cultivated human allies in secret during his time on Earth, Drag Strip has taken pains to secure one of his own. He considers the recruitment of a human to take care of the driving, no matter how loathsome the creatures might be, a perfect way to free up his own processor time to spend devising wicked plots against the Autobots - and there's nothing this cruel schemer likes better.
Of course, considering Master Disaster's somewhat... questionable appearance, Drag Strip may have decided he's already worn out his welcome.