> My question is: why do scientific papers use for-profit publishers
(such as Elsevier) AT ALL? Why not a nonprofit organization (Such do exist - like PLOS - but why does the other kind exist *at all*, much less be predominant)?
Happenstance of history. There is no good reason.
If one doesn't require print copies
The ICZN requires a certain (though small) number of "identical and durable copies", and the PhyloCode will require ink on paper. (Similar things hold, IIRC, for the ICBN and the ICNB.) But of course few scientific papers deal with nomenclature in the first place.