Working from home is the new casual Friday. It's one of those perks that many employers have incorporated into their policies, but it's still not the norm and most everyone wishes it were.
Employers have several reasons for wanting to limit the amount of work you do from home. They're not just being sourpusses about the situation, even if that's what you think. Most bosses who are hesitant to expand their telecommuting policies are afraid of giving employees too much room to mess up. Think about how many business casual experiments went awry when someone showed up in clothes more suitable for club-going. All you need is one blockhead to ruin it for everyone.