Most of these jeepneys are probably headed to Davao or Kidapawan, but they will wait until they have enough passengers to make the trip profitable.
In addition to hauling passengers from town to town, these Provincial Jeepneys are often used to haul goods too! For example, if there is a farmer in the Province, maybe some of his crops will be hauled on the Jeepney to Davao City and sold at the Public Market in Davao. The farmer can get much higher prices when he sells his produce at the big city compared to selling it in the smaller towns closer to where he grows the produce. That is why you will see these jeepneys carrying such products to the big cities!