Then I am not mistaken: the company was initially selling hardware, with the software being just a value add as you say (no copyright: no interest in trying to sell, exactly my point). Then, you were being paid for building software that (a) was probably not being made public anyway, and (b) would not have been of interest to others even if it were.
Even so, if someone came to your client and offered to take on the software maintenance for a much lower price, you might have lost your client entirely. This has very much happened to contractors in the past.
And my point is you couldn't have a Microsoft or Adobe or possibly even RedHat if you didn't have copyright protecting their business. So, you'd probably not have virtually any kind of consumer software.
We didn't charge maintenance for this software. We would write it to close the sale of a computer. It was treated as "cost of sale". I'm sure it was cheaper (to us) than the various discounts and kickbacks that happened in big mainframe deals.
As far as Microsoft and Adobe is concerned, I wouldn't regard it as a misfortune if they had never existed. I'm not convinced that RedHat's existence is contingent on copyright.