[raldi]

I would broaden the question beyond HN to society as a whole.

In 1990 it would have been considered normal and appropriate to clip an article out of a newspaper and post it on a communal corkboard. What are the key differences between that form of IP and others, and that analogy and the present situation of HN allowing archive links?

[layer8]

Reach, and ease of distribution.

[raldi]

Makes sense. If you mail a friend a clipping, or post it on the corkboard, only so many people are going to see it, but then even though posting the "clipping" to HN may feel like the same thing, it's hard to appreciate the massive change in scale.

As for ease of distribution, that might address OP's original question: It's easy to make and click an archive link, but it's a lot more effort to make or find a Pirate Bay link to another form of media, and for someone else to download and view it.