Maybe they do this because it creates better engagement? If they told you their signup process was quick, they would lessen their ability to convince you that

Maybe they do this because it creates better engagement? If they told you their signup process was quick, they would lessen their ability to convince you that you need to sign-up right now. If they told you what they did, then you wouldn't have to click through to their home page or twitter account to find out what it is. And finally if you weren't annoyed, you wouldn't have given them all of this free marketing on Hacker News.