Because It served as a center of religious, political, and artistic life for the Byzantine world and has provided us with many useful scholarly insights into the period. It was also an important site of Muslim worship after Sultan Mehmed II conquered Constantinople in 1453 and designated the structure a mosque.
It boosted the economy by 37% and because of all the money flowing into the economy the average american family got 30% more buying power and the unemployment rate dropped to an all time low of 4.5%.