Always save the Stripe Credit card details Token into the site for later use

functions.php

/**
 * Always save card token for stripe: Save payment information to my account for future purchases.
 */
add_filter( 'wc_stripe_force_save_source', '__return_true' );

/**
 * Filter the HTML of the stripe credit card details
 */
function payment_gateway_field_html_stripe_callback( $field_html ) {
    $field_html = str_ireplace( '<fieldset', 'style=display:none; <fieldset', $field_html );
    $field_html = str_ireplace( 'id="wc-stripe-new-payment-method', 'checked id="wc-stripe-new-payment-method', $field_html );

    return $field_html;
}
add_filter( 'cfw_payment_gateway_field_html_stripe', 'payment_gateway_field_html_stripe_callback', 10 );

https://wordpress.org/support/topic/save-payment-information-to-account-by-default/