The plausible reason has been explained by pc like half a dozen times in this thread. Checkout is not the only option. You can build a form from scratch if you

The plausible reason has been explained by pc like half a dozen times in this thread. Checkout is not the only option. You can build a form from scratch if you want customizability. Stripe is presenting developers with two options: one where they do the analysis and optimization and present you with a ready-to-go payment solution, and another where you can customize it to your heart's content. You (and others) are complaining because you can't customize the former option. This makes absolutely no sense.