Direct quote from your link, chimbu -
"Fixed-wing aircraft that are used for firebombing tend to be of the larger agricultural-style, specially modified for firebombing. These aircraft are sometimes referred to as SEATs (Single-Engined Air Tankers). This type of aircraft particularly suits the conditions most often encountered in Australia where there are relatively few long paved runways, but plenty of agricultural airstrips. "
When states sign 10 year leases on B737 aircraft, SEATS get parked.