Titles do not follow the usual rules of article usage.
The use of "The" in the main title of the article, "The Use of Articles in English Writing," shows it has more hierarchy than the subtitles and reflects how that phrase would be used in context, for example: This article deals with the use of articles in English writing. (It would be wrong to say: "deals with use of articles.")
Instead, the subtitles are treated like bullet points, where articles are usually done away with:
- Use of articles in science writing
- Use of articles with plural nouns