2 reasons for me:
1) High speed reliable Internet is not a thing where I live. I've tried telecommuting, but often had those days cut short by having to drive in anyways when my Internet went down.
2) The "If I can't see you, you're not working" people in the office
Regarding number 2, I've found that some people can get into the office at 6 AM and leave at 6 PM. They scurry around looking busy, busy, busy all day.
At the end of the day, they've often accomplished little or nothing. They can't focus on what needs to get done, getting distracted by every little thing. These folks would be better off just taking a moment to collect her thoughts, focus, and just get something done- but they never will, because that's the way they are wired.
Others are like me. We can get the same amount of work done usually in 2-4 focused hours. So yeah, my "work from home" usually includes half a day of actual work and half a day of playing with my dogs, cooking, surfing the net, or whatever the Hell I want.
Smart managers realize it's the amount and quality of the work produced, not "looking busy" that really matters. Unfortunately, there aren't very many smart managers.