"One of the ways readers receive and decode printed material is through the conventions that grow out of usage: capital letters in important places, italics in special places, quotations in small type, lists in a column, footnotes at the bottom of a page. The conventions increase in number and complexity for readers of scientific literature who learn to expect orderly citation of references, and common forms for abstracts, tables, figures, and mathematical display.
The purpose of a publication manual is to record and sometimes establish such conventions so that authors, editors, and printers may refer to it as a manuscript moves from typewriter to printing press" (pp. 577–578).
DeVivo, A. (1974). APA revises its Publication Manual. American Psychologist, 29(8), 577–580. https://doi.org/10.1037/h0038166