In Chapter 12, Diamond discusses societies developing writing through blueprint copying. He does not explicitly list reasons why some develop writing in this way while others do not. Therefore, we have to infer the reasons. We can do so by looking on page 228 in the paperback edition. There, Diamond talks about why blueprint copying might not be possible in some cases. He mentions the following reasons:
- The blueprint may be kept secret. If no one explains the new technology to you in detail, you might not be able to copy it.
- The blueprint may be incomprehensible to one who does not already know the technology.
- The invention may have arisen too far away and details might have become garbled.
From these things, we can infer that societies that engaged in blueprint copying were ones that were near to societies that invented technologies and that the inventing society was also willing to make the technology known to the people in the adopting society.