I can see the convenience in the Wh unit, because hours are so common and people prefer to think in terms of hours.
Joules and watts look nicer and are naturally fully compatible with each other. Non-technical people usually get very confused with kW and kWh, so switching to joules would create a clearer distinction between energy and power. Many energy production facilities also give their annual energy production in MWh per year, which mixes two time units in the same package!