In addition to other reasons, Alaska was accepted as a state either last or second-last -- I remember in the same year as Hawaii but I don't know if one was officially accepted before the other. I suspect that history would cause people in older generations to think of Alaska when there's a state to arbitrarily drop from some calculation and younger generations would mimic that tendency.
Alaska has been part of the US since just after the Civil War. It wasn't a state, but it was a recognized part of the US.
Because it's the largest state by far, so it's easier to do the math on. The next 3 biggest states put together don't add up to the size of Alaska. Alaska's land dedicated to national parks alone is bigger than the entire size of the land in each of the 23 of the 49 remaining states.
Alaska is like ~20% of the entire US area. It's the single largest state, which when removed, drops US from >1 million km^2 bigger than Brazil to 500k km^2 smaller than Brazil.
Even Americans don't realize just how freakin' huge Alaska is.