Why do plants do opposite breathing at night?

Many plants, called C3 and C4 plants, open their stomas during the day to let in carbon dioxide to instigate the process of cellular respiration. However some plants called CAM plants open their stomas at night. The main reason for this process is due to the physical environment the plants are located in. The majority of CAM plants are located in hot, dry and desert environments where water is scarce. As a result the CAM plants evolved so that they could close their stomas during the day and open them at night, to help retain water, at night the plants can still absorb CO2. Some examples of CAM plants are, cacti, pineApples, and aloe.