The people who write the questions for IELTS reading do something like this:
- They take a reading passage.
- They read through the passage and stop when they find something interesting.
- They make a question about that part of the passage, usually by paraphrasing it. For example, if the phrase "staff salaries" is used in the passage, the question writer might create a question with the words "employees' wages".
In other words, they use the "keyword technique" to write the questions, which is why you should use it to find the answers.