Why should coins be withdrawn from circulation?
1. Inconvenient storage and transportation. There is no space for coins in the pockets. They are heavy and easy to lose.
2. Unhygienic. Covid has shown us that the journey of money through our hands does not seem like an attractive idea.
Digital currency is only additional instrument. It can't be only one valid currency because it required electricity, telecommunications and devices. Real money doesn't require anything to get money or pay for someone. One little sun movement may deactivate satellites and internet may be not available for days. Imagine how the world look then without real currency.
Why should coins exist in the modern world?
1. It's a primary currency that doesn't require electricity, telecommunications and devices.2. Coins are of low value and, being of low value, perform their main function. E.g. we give children a few coins that they can save or spend.