8 foot beds do exist. They're very rare nowadays with nearly every truck being a super-extra-mega cab 4 door.
You generally have to find someone willing to sell you a fleet vehicle if you want a full 8 foot bed. Modern trucks are more like minivans with a vestigial bed sticking out of the back.
I have on old fleet truck: four full doors and an eight-foot bed. I love it, it’s getting quite old, and I have no idea how I’m ever going to replace it