Standards for Self Plagiarism
Proposals are tightly-controlled by rules. The only thing that really matters is legally handling the money. Different funding agencies often explicitly allow you to submit the same proposal. They will likely reject it anyway. If you get funding from both and you proposed the same thing, you will only be allowed to accept one of them (or else go to jail). 

Also many journals have a cutoff for incremental improvements, for example of 30 percent new material that is required. Given that number of submissions to journals has increased dramatically, this kind of requirement probably has as well, with many journals insisting on entirely new material. In ye olden days you could also get away with only a few references. Now your reference section needs to be some kind of tour de force of reference thoroughness too.

There is finally the issue of copyright and the (rather problematic) fact that journals want to sell our work as a product. Which we gave them for free. Plus helped them screen the products we would most want to buy for them. So they tend to push the motivation for demanding the text be as novel as possible, and now they have automatic tools to help enforce this. 

You'll note none of the above required the concept of "self-plagiarism", which I tend to think is an unnecessary concept we already have covered (when it actually makes sense) by other rules of ethics.