The same thing happened to TCP/IP stacks in the 90s (and multiple alternate transport protocols). They were initially separate products, sold by different companies. Then TCP/IP was bundled into the OS in ~Windows 3.1.

By today's lens you'd say TCP is part of the OS, but this wasn't the state of the world in the early 90s.

If you had disallowed bundling then, we would still be buying separate TCP stacks for our OS!