He's trailering the truck for two reasons: he wants to, and he can.
He can keep his truck on the trailer for storage, hitch up and go whenever he wants to race. Once he gets to the track all he has to do is unload and go. No changing from street tires to slicks, no dropping mufflers and exhaust system, and most importantly he doesn't have to worry about his street stuff growing legs and walking away while he's out racing.