Again, you seem to insist on an ulterior motive, completely discounting the value or pleasure of conversation. In contrast, reading is a solitary activity. Have you heard of book clubs? People read books, and then they get together to discuss the books.

Hacker News itself is all about reading articles, and then discussing the articles with others. "If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity."