Since it began, a lot of people were skeptical that the open source movement would impose over proprietary software. People thought keeping everything hidden and proprietary was the way they could differentiate.
The Unpatent Manifesto
Luis Cuende

I need to point out a few facts in the open source vs. proprietary software war, because actually things did not happen in the way or for the reasons many people think.

In the early days of software engineering, back in the 50s and 60s, source code was generally distributed with the software, providing the ability to fix bugs or add new functions. Source code was not seen as a commodity itself.

Users also feared that programs that did not come with source code would contain backdoors that granted the distributor attack to their system, as security mechanisms were virtually nonexistent.

Many of the modifications were openly shared in keeping with the principles of sharing knowledge, and organizations sprung up to facilitate sharing.

In fact, prior to 1974, software was not eligible for copyright under US Law and therefore it was always in public domain.

Nevertheless, as operating systems and programming language compilers evolved, software production costs were dramatically increasing. A growing software industry was competing with the hardware manufacturers’ bundled software products. That is the only reason why, in the late 1970s and early 1980s, computer vendors and software-only companies began routinely charging for software licenses.

As you can see, from a historical perspective, open source came not for disrupting the industry but to recover viable business models that were already profitable without the need to restrict individuals’ very own right and freedom to run, copy, distribute, study, change and improve the software.