Reason One: Spontaneous and fun
"Crossing the Creek"
Reason Two: Very bright saturated colors
Reason Three: Easy to control light/darkness
Reason Four: Shows expressive strokes
Reason Five: Easy to change in midstream
Reason Six: Dry Pigment, no mixing, what you see is what you get
Drawbacks: Expensive and need to be protected from damage by framing.
Allergies, pigment dust