When they use a model incorporating the two features, the physicists demonstrate that they are responsible for the power-law scaling observed in many complex systems. It's rather like the highly traveled interstate highways becoming more traveled as the traffic on the less-traveled country roads remains about the same.
Physicists observe a similar pattern when water freezes and becomes ice.
Barabasi explains that knowing these facts about the Web is important because it's telling us that the Web is very inhomogenous. The power-law scaling of the Web was a complete surprise. People who want to build efficient search engines need to be aware of the inhomogenous nature of the Web, that they going to have to keep going back to the central hubs to reach other sites.