Working on repetitive tasks in a cubicle in front of a computer is perfect for that. In today's workplace not much is expected of workers in return for a high salary. With telecommuting, many dot-commers don't even have to leave their houses, or they only have to go into work a few days a week. It's really hard to tell if someone is high just by reading an e-mail. I've never even met, people who would never know I was a junkie.
Virtual life makes it so much easier to get away with things.
And if you don't like your job, or office politics are bad, then heroin is a total escape. You can deal with anyone. Nothing matters anymore. A sure sign of someone high on dope is the pinned eyes. Speed, coke, and ecstasy all make your pupils big, while heroin makes them pinpricks.