Heat travels from hot areas to cold ones. During hot days, the walls and concrete roof exposed to the sun absorb heat from outside. The heated top emits heat in the building creating an uncomfortably hot environment.
Due to the bricks and concrete heat capacity, the walls and roof retain heat during the night making the inside of the building very hot. During winter, the walls and rooftop of the house absorb the heat that one needs, emitting it outside the home. Occupants of a building are therefore exposed to chilling temperature, feeling like they are outside.
To curb all these extreme weather changes that make spaces uncomfortable, you need good insulation.