The software code is free, but you get a lot more than software bits and bytes with a Red Hat subscription.       
Anyone is free to identify and download any or all of a vast number of individual components from a wide range of contributors that could comprise a Linux operating system. Of course, you would then have to sort, examine, test, integrate, harden, and support a custom.

Linux solution for your company. You would work with many software and hardware vendors to support your Linux distribution. You also would have to hire the IT
staff to create, support, and maintain your Linux distribution. Most customers find the expense, distraction, and increased security risk to be unappealing.
Purchasing a subscription to Red Hat Enterprise Linux lets you concentrate on projects specific to your business.