Demo trading before starting the real trading would be very beneficial for a newbie who even didn't know about trading. First he have to learn more things in that trading and then he have to take a better yield profit in order to make its own profit...
Of course, demo trading is useful for beginners, but you don't need to exaggerate its value either. As long as the losses are virtual, the trader will not be able to assess all the risks associated with trading. And only the real loss of his money when trading will force him to take up training again in order to minimize losses and accordingly make a profit.
While it could be considered useful for beginners, but it’s never a compulsory. Some few traders still manage to trade successfully without going through demo trading. Experience has molded them to be more skilled and proficient traders, and of course with patience that is necessary when trading.