Lack of armour, poor load carrying capacity and from my understanding a bit temperamental for use by military forces are factors against their use.
Most of what they do can be done nearly as well by a standard Landrover or Landcruiser 4x4 much more cheaply and 'cause they are standard vehicles require less support. The Chadians did very well with just Landcruisers against the Libyans in the 1980s. Shades of "Rat Patrol" for the older members.