If you add following code to the file
/wp-content/plugins/woocommerce-gateway-stripe/includes/class-wc-gateway-stripe.php
public function save_payment_method_checkbox() {
printf(
'<p class="form-row woocommerce-SavedPaymentMethods-saveNew">
<input id="wc-%1$s-new-payment-method" name="wc-%1$s-new-payment-method" type="checkbox" checked="checked" value="true" style="width:auto;" />
<label for="wc-%1$s-new-payment-method" style="display:inline;">%2$s</label>
</p>',
esc_attr( $this->id ),
esc_html__( 'Save to account', 'woocommerce' )
);
}
It would be automatically checked but no idea if it would work or not you will have to test it if it works you can hide that by css