They don't understand the model where SaaS businesses use Shopify as a billing channel on top of their own subscription model, it's all or nothing - they assume that anything in the app store can only use Shopify billing if the user installs via Shopify, which is fair but their billing API has glaring issues:
- App Charges get added to clients bills, you're not getting paid right away (60+ days in some cases) vs getting paid instantly
- If someone doesn't pay their Shopify bill, tough shit you're not getting paid
- Got fraudulent accounts billing via Shopify? They can use your app then never pay anything - fun
- Want to do refunds? Too bad there's no way to do it via the API you have to manually email Shopify then they apply an App Credit (not even a refund) for the customer, then you email them back
- Uninstalling the Shopify App cancels billing, so you lose complete control of your normal downgrade process
- Payments come via PayPal bi monthly :(
There's plenty more, but you're basically losing all the upside of Stripe in exchange for the App Store promotion of your app.
The audiobook is also really well narrated.