At some time, using desktop video conferencing may not be correct method of communication. There may be times when your presence will be needed on site or at a different location. A crisis may occur which can not be resolved using desktop video conferencing. You may need to collaborate with more people than you can use on the video at one time. These are just a few of the disadvantages.
Many situations arise on short notice.
Things happen you can't prevent. When this does occur you can rest assured that the best choice is the desktop videoconference. You can set it up with very little notice and have a chat with someone or several people in another state. I personally have seen this type of communication used in the military when it urgent that a conference was needed immediately. When urgent situations arise, this is the best time to use desktop video conferencing.