Conversational writing kicks formal writing’s ass:

What most people mean when they say "write the way you talk" is something like, "the way you talk when you’re explaining something to a friend, filtering out the ’um’, ’you know’, and ’er’ parts, and editing for the way you wish you’d said it." […]

So one of the theories on why speaking directly to the user is more effective than a more formal lecture tone is that the user’s brain thinks it’s in a conversation, and therefore has to pay more attention to hold up its end! Sure, your brain intellectually knows it isn’t having a face-to-face conversation, but at some level, your brain wakes up when its being talked with as opposed to talked at. And the word "you" can sometimes make all the difference.