It's funny but Japanese people like to see long lines. Why? Because it proves that whatever they are in line for is popular or something of great value. This may be one element of the Japanese culture, since most Japanese automatically assume and believe that long waits are worthwhile. It could be a restaurant, apparel shop, souvenir shop, or even a wait for a particular object. Whatever it is, people from the states or other countries may find it interesting, because they constantly try to get away from long waits.
For example, Krispy Kreme Doughnuts came to Japan 2 years ago, and you may not believe it but people would wait in line for 2 hours to get a single doughnut. They do not complain about the long waits; they patiently wait until their turn to purchase. In fact, most are excited to finally try out the doughnuts that they do not mind the waiting at all. As they finally get the doughnut, they are satisfied, and it makes them happy as they became one of the members that ate the famous "Krispy Kreme Doughnut."
If you ever see a long line in Japan, it is probably worthwhile to join the line or see what they are waiting for, as it is probably for something currently famous and popular.