Many WooCommerce stores have both WooCommerce ‘Products’ and ‘Subscriptions’ in the store. These are different product types.
In some cases, a ‘product’ added to the customer’s cart might be unnecessary if they have added a ‘subscription’ that includes access to that product. Imagine a customer has added an industry report (a simple virtual and downloadable product) to their cart for purchase. Then, that customer sees that by purchasing a ‘subscription’ (subscription product) they can get access to the original report and every other on the site. So, the customer adds the subscription product to the cart.
Once the subscription is added to the cart, you may want to have any individual products included in the subscription automatically removed from the cart. This makes life easier for the customer– they won’t accidentally purchase access to the same product twice.
In WooCommerce, this scenario is called a “Mixed Checkout.”