"Nothing compares to the simple pleasure of ringing your bell while cycling away from a horde of mutants" - Anonymous survivorThe bicycle is a one person vehicle. It needs no parts, is immediately rideable, and has no inventory to speak of.
It has a low top speed but reaches its top speed very fast, and is relatively nimble in terms of maneuverabilty.
Beside the lack of an inventory and the absence of player protection from ranged attacks, the biggest advantage the bike has is that it needs no parts to run, and can climb steep slopes very efficiently, even faster than a 5-ton Truck, or Bus. It is also relatively indestructible.
Bicycles have their own spawnpoint types, so destroying a bike will not allow for the spawning of a motorized vehicle