Out-of-band data.

While onsite, internal centers may theoretically have precisely the same access to data that virtual and external centers do, it's the out-of-band data - the information which isn't measured - which provides the difference.

A center manned by direct employees of an organization often has the advantage that the staff feel more responsibility and connection to the rest of the company. There might be a higher proportion who actually transferred from other departments, or are looking for promotion to them. They may well use the same cafeteria or lunch room. They have an emotional, financial, and sometimes moral stake in doing the best they can to keep the heat off their fellow employees. It's personal.

Someone who never sees anyone else from any other area of the company they're providing support for doesn't have that connection. It's a known glitch in permanent telecommuting. And if they're simply a contractor through a third party, especially if they're providing call services for multiple different companies, there's no personal reason to go above and beyond.

Virtual platforms are a great way to connect the person under the headset to whatever systems and data they need, and they can be a godsend if you need to be able to swiftly alter the geographic distribution of call center employees or handle telecommuting, work-at-home-during-blizzard conditions, or sending someone out to be an onsite set of eyes when there isn't a specialized office available for them. It means that there are a lot more options available. But few employers are going to jump straight to a completely virtual setup unless they're already heavily outsourced in that area.

Virtualisation would seem to work best when combined with companies which have extended needs and scope for their call centers, companies looking to implement backup and disaster recovery systems, and companies looking to go partially virtual while still retaining the psychological bonds of personal face-to-face interactions during break times. It's the same reason teleconferencing hasn't completely replaced jet flights to interstate and international meetings.