Magento – How to add New payment method (credit card) in magento 2

The main reason would be security of your customer's information. If anything where to happen with the credit card information you could be held liable.

Being PCI Compliant goes well beyond having an encrypted database. You can find all the information about PCI Compliance here

Dan

www.ecommercewebsites.biz

Yes, you can retrieve credit card details from order.

$order is of type Magento\Sales\Model\Order

The following methods get the credit card details:

$order->getPayment()->getCcExpMonth(); 
$order->getPayment()->getCcExpYear();
$order->getPayment()->getCcLast4();