Because you don't have to write code on a whiteboard with someone staring at you in your daily work. You're free to sit alone, make a stupid off-by-one error, m

Because you don't have to write code on a whiteboard with someone staring at you in your daily work. You're free to sit alone, make a stupid off-by-one error, misspell a var without feeling like you'll be fired for it. Technical discussions at work aren't so high-stakes as ones in an interview. If you do badly in an interview, you've wasted an entire day for nothing. If you fail to speak in a technical discussion at work, best case no one notices, worst case they think "Hm. Looks like Brian didn't get much sleep last night". Just the knowledge of these stakes can affect your performance.