Why is their no Squirrel Hunting allowed in Idaho?

The information copied below lists many of the animals that may be hunted and those that may not be hunted.   Hunting of Predatory & Unprotected Animals (MAY BE HUNTED--HUNTING OR TRAPPING LICENSE REQUIRED) Some animals are classified as “predators” or as “unprotected” and can be hunted and taken all year. Animals classified as predators in Idaho include coyotes, raccoons, jackrabbits, skunks, weasels, and starling. The most frequently hunted unprotected animals include marmots, fox squirrels, porcupines and Columbian ground squirrels, English sparrows, Eurasian-collared doves, and feral pigeons. These species may be taken in any amounts and at any time by holders of the appropriate valid Idaho hunting, trapping or combination hunting license, provided such taking is not in violation of state, county, or city laws, ordinances or regulations. Game birds may be taken only in accordance with established hunting rules. Protected  Nongame Wildlife, Species of Special Concern, Threatened or Endangered Species, Protected Birds (MAY NOT BE HUNTED) Special classifications for some animals extend extra protection to those species. These animals cannot be hunted, taken or possessed. Threatened or endangered wildlife include caribou, Canada lynx, grizzly bear, and Northern Idaho ground squirrel. Protected nongame wildlife include red (pine) squirrel, wolverine, chipmunks, rock squirrel, Wyoming ground squirrel (nevadensis subspecies only), golden-mantled ground squirrel, Merriam’s ground squirrel, Piute ground squirrel, pika, kit fox, northern flying squirrel, bats, Southern Idaho ground squirrel and migratory song birds. See page 44 of the Upland Game Rules book for ground squirrel  information.  All birds in Idaho are protected except starlings, Eurasian-collared doves, English sparrows and feral pigeons. Protected nongame birds cannot be hunted, taken or possessed (including parts of birds, even if  found dead). All hawks, owls, eagles and vultures are protected.