There are 3 main reasons:
1) Cloth diapers are friendly to the wallet. As each disposable diaper costs $0.35 to $0.50, you can save up to $1,000 a year using cloth diapers, compared to disposable diapers.
2) Prevents diaper rash. Cloth diapers are chemical-free, hence they do not cause chemical reactions in baby's skin.
3) Environmental friendly. Babies use up to 7,000 disposable diapers in their 3 years. These disposable diapers are not biodegradable, causing many landfill problems and air pollutants harmful to human health. You, too, can play a part. Each cloth diaper we use helps to preserve the environment for our future generations!
You can read more about it in detail here:
Advantages of Cloth Diapers