The first and foremost reason is leakages which are caused due to joints in the roof. If it is a sloping roof than chances are there at the joints and junctions. One of the reason why roof tiles break is simple wear and tear. In addition to wear and tear, harsh weather conditions may cause tiles to fall apart. If it is a flat roof, chances of leakages are due to poor workmanship or due to cold joints in the concrete.
If the roofs are made up of Asbestos Cement Sheet of other Polycarbonate materials than chances of leakages are due to joints getting loosen due to wind. Also sometimes the connecting screws get loosen up making up the holes bigger creating leakages. Another reason is that if the damaged roof tiles are not taken care of, water can seep into a roof and eventually, any water that has accumulated underneath roof tiles will seep into beams, through ceilings, and into a home.