Because they're paying for a platform to deliver services and the platform then tries to dictate how they run their business. It's questionable at best and should perhaps be illegal.
OP is not "paying for a platform" on Shopify -- they are not a customer of Shopify running a store. OP is a Shopify partner offering a service to Shopify's clients, through Shopify's own web site, and is expected to pay Shopify a cut of their profits in exchange for being featured this way. This is a standard practice for this type of partnership.
OP is not "paying for a platform" on Shopify -- they are not a customer of Shopify running a store. OP is a Shopify partner offering a service to Shopify's clients, through Shopify's own web site, and is expected to pay Shopify a cut of their profits in exchange for being featured this way. This is a standard practice for this type of partnership.