A professor's life has many responsibilities. Teaching and research of course but also paper writing, grant proposals, meeting with students, and administrative tasks including seemingly endless committee meetings. When I visit another university I leave most of these responsibilities behind so I can focus on research. I also expect the people who invited me to make time in their schedules so we can work together. That way even a short visit can be quite productive.
As the length of the visit increases it becomes harder to avoid these other responsibilities and the amount of research time per day decreases. In the extreme, two people who work at the same university for years end up spending very little time talking research together.
This explains why teleconferencing will never replace traveling no matter how technologically advanced. The social requirements of a short visit require people to spend time together in ways a teleconference cannot. What teleconferencing will do is "allow" me to attend those endless committee meetings wherever I am.