It's a matter of isolation. Working from home takes away the ability for you to walk over to someone's desk/office and have a quick chat or go over a problem that may be difficult to cover via email or IM. And no matter how accessible you try to make yourself, when you're working from home, the distance barrier means that your coworkers won't consider you as someone to contact easily. It also means people are more likely to forget to pass on information because when they don't see you, they don't think about you as much.
You've just marked yourself as somebody who is very likely still in college and/or under the age of 25 and/or does not have spouse and kids and dog and cat, etc. :)
I submit that properly trained, "spouse and kids and dog and cat" aren't disruptive. I have all of those but a dog and work at home for hours at a time without interruption.
Private offices still have the potential for in-person interruptions. Working from home usually requires electronic communication to get ahold of somebody, which is much easier to defer if you're in the middle of working.
I'm wondering whether you mean a work area where each employee has his own office, or an office for an independent programmer without coworkers. The latter might be similar to home working, though without the casualness (coding while undressed) or ability to attend to home/family tasks at the same time.