Abody having uniform velocity has zero acceleration. why?

Acceleration is defined as the change of velocity with respect to time. The formula for acceleration is:
a=(Vf-Vi)/t
where: 
a = acceleration
Vf = final velocity
Vi = initial velocity
t = time in seconds (s)

At uniform velocity, where there is no change in speed and direction,  the final velocity (Vf) is equal to (Vi).
If Vf = Vi, the rate of change in velocity (Vf - Vi) is zero (0).

a = (Vf - Vi) / t
a = 0 / t
a = 0