Certified GKH Gardening Expert
Sometimes, in warmer climates, it can be difficult to keep enough moisture in the soil during the summer. When the plants drink the water faster and evaporation is high, it makes for a difficult situation. The plants will not get enough water.
Some plants, in some places, will need this. This will not be common practice for most places, but can be necessary in the South, or in zone 7 and above in general. This is especially true in warm areas that don't get much natural rain.