Why is that? Well, we 9/11 Truthers would say that WTC7 was an embarrassment to the power establishment of America. It pointed to a darker truth that they preferred not be seen by the general public. All pressure was brought to bear on the media to make sure that no further film of Building 7's collapse would be seen or talked about. Now maybe we Truthers are wrong about the motives of the media. But the point remains that except for the internet and something called "Youtube," Building #7 would have meant little to most people. (I'm curious how many people have heard of it, even with youtube. I would guess it's still a minority).
So what does this have to do with Jesus? Mythicists -- people who believe that Jesus of Nazareth did not exist -- like to point to the dearth of testimony regarding Jesus's life. For example, Philo, an Alexandrian Jewish leader and intellectual, and contemporary of Jesus, writes
But could there be another reason why Philo never mentioned Jesus? Could it be that Philo had heard all the rumors about Jesus, and his supposed miracles, and his supposed resurrection, and the nascent movement growing around him, and decided not to take any of it seriously? Could it be that Philo decided that it was just another one of those weird religious cults that occassionally pops up, gains some momentary popularity, and then dies off? Why would it be worth mentioning along with the really important things, such as politics and philosophy? Perhaps Jesus was to Philo what Building 7 is to most people today: An odd curiosity, not to be taken seriously.
*To be honest, I haven't read anything by Philo, so I'm not sure how much he did write about Jewish life in first century Palestine. The impression I get is that Philo was more of a philosopher and less of an historian, unlike Josephus, who tried to give many historical details about first century Palestine. But I'm willing to bet that Philo wrote something about it.