Here are a few observations made at least in my wife's department. Keep in mind her department is all backroom loan processing - basically little to zero contact with customers/clients and all correspondence inner office.
1. The people who are inefficient working at home are also the lower producers working in office. They are slower in general, and working from home nets the same results or worse. I can only assume the technology slows them down, or they also are easily distracted.
2. I will say the "answering of phones" became an issue. These are not calls from superiors being missed, but from other employees in the same department. Most of these missed calls are from employees who fall into #1 above. The employees being called are the high producers annoyed that they are having to explain something to a shitty employee that could be resolved in an email.
3. Work from home offered employees ease of working after hours which helped a bunch. I'd argue it got a lot of employees out of the stupid "clock in, clock out" 9-5 mindset. Obviously with that there is give and take.
My business is not large, so managing all of this is pretty easy. I know what my employees are accomplishing, but I hire better employees and pay more than competitors. If you can't trust employees working from home, how the hell are you trusting them to work for you at all?