Why can't motivations in a paper's introduction be copied? I'm always baffled that the preamble in introductions in scientific papers is pretty much always the same for papers dealing with the same topic. And yet, no two papers have the same introduction, since doing so would be plagiarism. Even worse, one cannot even copy this preamble from papers one has already written, as paper reviews are anonymous, so reviewers cannot know whether the author is plagiarizing or copying his/her own work.

At the same time, this feels like a huge waste of time, akin to writing essays in high school, where you have to paraphrase and write X number of words just to fill in the page.

Talking with other academics, this is pretty much a pain point for everyone, which not only annoys the writers, but also the readers, who must skip useless text every time they begin a new paper.

I guess a simple reference to a specific introduction is not enough, as a paper needs to stand to its own (if it even makes sense in this context), but why is it so ingrained that such text must be written and rewritten, ad infinitum, in a Sisyphean effort?

EDIT: Please note that I'm talking about just the preamble of the introduction. It makes sense that overall the introduction needs to be tailored on your specific contribution. But often papers start with a brief description of the field/topic it contributes to, the field's practical applicability, and possibly some related work that makes the field look good. The preamble is just the hook needed to place one's own contribution in an overall context (also to explain the topic to somebody who may have stumbled upon the paper), but at the same time there is no real requirement that it be rewritten new every time. So why?

As an example, consider, as posted in a comment, this preamble:

Hedgehog hunting is an important problem in ecology. While the typical procedure consists of a) tracking, b) sniffing, c) aiming, d) shooting, e) desugaring, f) acquisition, the role of the spikes in sniffing did not come into the spotlight before the seminal work of Whippet et al. (2007). In this work we propose a radically different approach to hedgehog spike treatment by invoking desugaring before sniffling.

But if I wanted to write about using metal spikes, you see that the first sentence wouldn't really need to change. And such preambles can usually take a whole paragraph or two, which makes the rewriting annoyance pretty big.
At a fundamental level, every new paper is (or should be) presenting something new, whether it be new results, methods, experiments or even summaries or reviews. The paper would be redundant if it didn't present something new.

The 'introduction' or 'motivation' section follows the title and abstract as the next link in the chain to motivate people to read your paper in its entirety. Since it's your paper that you want to motivate people to read, it doesn't make sense to copy the words intended to motivate people to read some other paper.

There may be parts that overlap with prior work (and other answers on the site suggest methods to deal with that), but if you want your motivation section to relate to the novel elements of your paper, it needs to be recast for each new paper.

Your question (especially per your update) is why this boilerplate text can't be either copied or left out altogether.

When I'm presented with a paper, I am not always motivated to read it at first, so it doesn't help for the author to jump straight to the equations or experimental results, etc. What does help is to start with common ground. This is the job of the preamble. You can't leave it out altogether for the same reason libraries include the first part of each book's Dewey Decimal Number on every book - it's needed when the work is separated from the collection.

As for copying, it's a matter of skill in the craft to keep it concise, yet useful:


  No one prevents you from copying a few sentences from your previous papers. Except that perhaps page/word limits will encourage you to jump as quickly as possible to your actual contribution. – Alexey B