IP videoconferencing in the business world typically consists of dedicated videoconferencing equipment which operates purely over the internet (as opposed to early technology videoconferencing which operated over public or dedicated phone lines). It is entirely possible to do it from home if you have a broadband internet connection, a dedicated external IP address (required in many cases) and equipment that is compatible with the person you are trying to connect with. While there are some common standards out there and the problem is nowhere near as bad as it once was, there are some lingering issues with compatibility between equipment.
Most webcams, however, aren't going to work because they lack the necessary software to make the connection and will not provide the level of stability and quality needed. The dedicated equipment and/or software is typically quite expensive. The company likely gave directly to go to the center because they knew it was already set up and would work. A company is not going to be patient with an interviewee if you spend the first 10 or 15 minutes trying to establish the connection.