Because a Linux distributions are used all over the world. Stripe and PayPal are good, but insufficient as a choice - one can't be expected to pick SDKs that wo

Because a Linux distributions are used all over the world. Stripe and PayPal are good, but insufficient as a choice - one can't be expected to pick SDKs that work equally well in all regions, preferring local payment options, registering with local tax authorities etc. Also, Stripe and PayPal don't offer tools to check if an app is running with a valid license/subscription, it's not pirated etc. (the equivalent of the App Store receipt signature).