What is the advantage of flat roof comparing with the pitched roof?

There are several advantages:

- The area of a flat roof is less than a pitched one therefore the material will be less expensive;
- labor costs at installation are considerably smaller, especially at roofing works on high structures; 
- there is the possibility to equip the flat roof for the terrace, the observation deck, lawn; 
- air conditioners, antennas, space elevators will not spoil the facade and destroy the architectural integrity of the building