Why headlines that aren't questions don't need to start with "Why"

It's unnecessary. An article is expected to explain "why". How did this odd trend catch on? Some recent examples from HN: "Why Sleep Apnea Patients Rely on a CPAP Machine Hacker" -> "Sleep Apnea Patients Rely on a CPAP Machine Hacker" "Why the world needs deep generalists, not specialists" -> "The world needs deep generalists, not specialists" "Why I’m Giving $1.8B for College Financial Aid" -> "I’m Giving $1.8B for College Financial Aid" "Why We Need Difficult Books" -> "We Need Difficult Books" "Why we rolled our own consensus algorithm" -> "We rolled our own consensus algorithm" "Why Facebook's API starts with a for loop" -> "Facebook's API starts with a for loop" "Why 536 was ‘the worst year to be alive’" -> "536 was ‘the worst year to be alive’" "Why affordable housing is scarce in progressive cities" -> "Affordable housing is scarce in progressive cities" "Why you shouldn't “work remotely”" -> "You shouldn't “work remotely”" "Why Google can’t technically do customer support (2011)" -> "Google can’t technically do customer support (2011)" "Why New York Is Resorting to Paying Amazon for What Google Will Do for Free" -> "New York Is Resorting to Paying Amazon for What Google Will Do for Free" "Why You Should Use a Text Area for Address Form Fields" -> "You Should Use a Text Area for Address Form Fields" "Why Standing Desks Are Overrated" -> "Standing Desks Are Overrated" "Why I Left My Big Fancy Tech Job and Wrote a Book" -> "I Left My Big Fancy Tech Job and Wrote a Book"