Because it symbolizes so many different things and inspires us to believe in our faith and in JESUS (the SON OF GOD). He died a painful crucifixtion so that our sins would be forgiven. His resurrection is a sign that death will not conquer life. Through JESUS (as long as we believe) will have life eternal.

All of the events that transpired immediately following JESUS' death were not of coincidence. These events were done at the hand of the LORD to lay claim that JESUS was no ordinary man. This was done so there would be no doubt that JESUS was in fact the SON of GOD (whether the people wanted to believe it or not). The Centurian was one who believed and knew that he was guilty (like many) for putting JESUS to death.

Throughout JESUS' ministry he conducted many miracles. Perhaps, those who passed by and mocked JESUS were hoping for one last miracle (the ability of JESUS to remove himselt from the cross so they might believe). What they didn't realize through their waivering faith was this was not in accordance to the scriptures. Hence, their lack of faith and perhaps their lack of fear in GOD caused them to mock JESUS in this manner.