When you are using a standard phone system, your customers are more likely to hear a busy tone when all your phones are in use. When this happens, your prospects can end up looking for another restaurant, and you miss out on multiple sales opportunities.
This situation never happens when you are using a VoIP system. When all your phones are in use when placing orders, your customers will be put on hold and listen to music, allowing you to provide your customers with a better customer experience. As a result, you can have better chances of improving your sales and boosting your revenue.