It's a hangover from the Defence of the Realm Act (DORA) from the IWW. The clocks were forcibly changed then to enable higher production levels in both munitions and agriculture, plus the minimisation of accidents due to blackouts. In addition, there was a huge concern about the workers drinking and losing hours, so you can blame DORA for the licensing hours as well.
There is no real need for it now, it's a relatively new thing. It should be able to be changed now as is reasonable.