1: Don't have enamels or oils to make a wash from.
2: Don't have the appropriate thinner to make the wash from.
3: Don't have a well-ventilated area for using said thinners safely.
4: Too young to use said thinners safely unsupervised.
Whereas if you have acrylics and tap water you can make a basic acrylic wash in perfect safety.
Having said that, yes, enamel and oil washes can deliver superior results once mastered.