Taxying with the engine off does seem a bit of a risk for several reasons, as already mentioned, another is that you have lost the ability to give a blast of power and a boot full of rudder to make a turn.
Also people cannot hear you coming, perhaps unlikely on a noisy ramp but possible. Many many moons ago at LHR I was working on the ramp when I heard a squeak, squeak, squeak and looking up the LHR/LGW shuttle BN Islander was taxying towards me and its parking slot with both engines stopped, the only sound was its squeaky brakes.

Richard