> I very much doubt the company [...] was selling the non-copyrighted software
Well you'd be mistaken. Lately, it was custom software, for a particular client, and of no interest to others. Earlier, it was before software copyright was a thing, and computer manufacturers gave software away to sell the hardware.
At the very beginning, yes, it was "very specific" hardware; it was Burroughs hardware, which used Burroughs processors. But that was before microprocessors, and all hardware was "very specific".
> (plus they rely on trademark laws and design patents quite often)
Craftsmen and labourers were earning a living long before anyone had the idea of a "trademark", still less a "design patent".
> The output of lawyers is in fact sometimes copyrighted
You're right. That's why I didn't say "lawyers", I said "legal advocates". Those are people who speak on your behalf in courts of law, not scribes writing contracts. Anyway, the ancient Greeks and Romans had written laws, contracts and so on; they managed without trademarks and copyrights.