No, you do not necessarily have to create a user account to place an order in the NSW eShop!
The purchase of items for which the legislature has provided for a regulation (e.g. age limit) requires the creation of a user account.
If there is a product in your shopping cart at the end of your purchase that requires a user account to order, you will be informed of this before the payment process. In this case, you can create a user account to complete the ordering process or remove the item in question from your shopping cart.