Never.
Really not ever if you need to ask this question.
If you are building a new shopping experience, you likely aren’t really asking this question.
If you simply want to sell stuff online, do not go build a front end, payment system, taxation system, inventory management, temporary sales management, email collection, analytics, reviews, tags, discount codes, shopping cart, in-store blog with an authoring system, SEO optimization for images and links, and more just so you can sell your hand made soaps.
Put the keyboard down, use this Shopify referral link, sell your wares.