Thinking like this is how we ended up with a panic about Y2K. Programmers in the 1970s and 80s could not conceive that their code would still be running in 2000.
The computing industry was in a huge amount of flux in the 1970s. How many bits are in a byte? Not a settled question. Code was being rewritten for new platforms all the time. Imagining that some design decisions would last for decades probably seemed laughable.
