Hi,
That's because of the way the stripe API we're using in the payment plugin is done.
It requires to perform a javascript call to Stripe when validating the credit card form on the page.
If you want a one page checkout with the credti card form on the same page, you need to use another payment gateway like Authorize.net in AIM mode, PayPal Pro, etc.
If you want to do it with stripe, I think it will require the development of a new payment plugin for Stripe with another API of Stripe which can work within the constraints of the checkout, like the other payment gateways.
So you'll have to contact a developer to work on that for you.