They allow for selective reading of text material. Topical headings like Introduction, Discussion, Results, and Summary are helpful. However, descriptive headings like Purpose of the Study, Analysis of Survey Responses, or Data Retrieval and Implementation Programs are even more effective because each specifically defines the content of the section that follows. White space around text draws a reader's attention and also helps make the page look less cluttered. The single-sentence paragraph is a variation of the white space technique.
Readers tend to read single-sentence paragraphs because they look easy to read and understand.
Using too many single-sentence paragraphs, however, diminishes the emphasis and interferes with the flow of the text. Lists are visually emphatic because they have numbers, letters, bullets, or dashes to define each listed item.