When you need a catalog rather than a store
A catalog is a product showcase without a cart or payments. You need it when the deal goes through a manager anyway: in B2B, when selling equipment, spare parts or building materials.
What matters to the customer is finding the right item, comparing specs and sending a request. Online payment does not fit that flow — prices are often individual and depend on volume.
If you sell retail at fixed prices, you need an online store with a cart and payments.