When the guys from Shiny started designing our beloved MDK1, they decide to put there some kind of vehicle. The appearance resembles a motorcycle :



It seems that the arenas were to be much, much bigger than normal.
Motorcycle probably served to move between different arenas. Quite possible that the vehicle was also intended to eliminate Stream Riders.

What do you think about it? It is good that the creators have removed it from the game?

Vehicles would not work well in MDK, and it would probably (back in 1997) be impossible to create good vehicular gameplay.

Dont know really. The arenas were quite large, especially in 4th level so you could use some wheels there. But as Michaelosaur says, that would be hardly possible in with the MDK engine.