That's a GOOD question Rex. Heck, even Shadow riding a vehicle was unnecessary for him in Shadow The Hedgehog AND Sonic The Hedgehog 2006! Why DOES Shadow need a vehicle to drive if he's fast compared to Sonic?!
A Blue Hedgehog who runs at the speed of sound...
A genderless Nightmaren who flies in Nightopia...
A Shooting Star who flies around the Valdi System...
A human boy who uses his legendary chicken suit...
A Rudie skater who sprays Graffiti around the city...
Together...They'll be unstoppable...