If you need all the orders and all the customers sure.

But usually you need some of the orders and you need the customer info associated with them. Often the set of orders you’re interested in might even be filtered by attributes of the customers they belong to.

The decision of whether to normalize our results of a database query into separate sets of orders and customers, or to return a single joined dataset of orders with customer data attached, is completely orthogonal to the decision of whether to join data in the database.