Because for a while it was accurate, and the usage stuck even after it changed (Alaska was admitted before Hawai’i.)
A similar reason a large swath of the north-central part of the continental US is called the Midwest. (In Census uses, where the smaller divisions have more modern/accurate names, this is ironic because the Midwest region consists of the West North Central and East North Central divisions.)
It does come up when discussing shipping and transportation, but Alaska and Hawaii also each have a distinct enough culture and distinctly different set of challenges. Every State along the Colorado river is part of an interstate compact to manage water rights, but if Alaska has a dispute with British Columbia over some resource along their borders, that’s an international matter that pulls in the Department of State and Canada’s, Foreign Office? I know some of the British offices but I’m actually not familiar with Canada’s government agency nomenclature.