What makes a person want to create a computer virus?

Of all the things that people could do, why is creating a virus that sends people into a panic and causes widespread havoc on that list of things? Recently, there was a new virus that can actually be spread through USB flash drives, and steals pwords (or something close to that). What could possibly posses a person to make something that has the potential to mess up thousands of computers and costing the computer owners money? Its crazy. Please, provide your input.