It has been 220V in the past and was upped to 230V because higher voltages make it possible to transport more energy with less losses.

Appliances that were built for 220V also work with 230V, although they sometimes are less efficient or have a lower life expectancy. To us consumers 220/230V labels are only relevant to distinguish them from 110/115V and low voltage systems.

And 230 V is an International Standard.