Why are the cruiser weights soo tall?

Question

enzo 6 foot 4

cunningham 6 foot 3

david haye 6 foot 3

i mean why dont they move up? are they scared or something?

i think cunningham makes a great heavyweight i mean 82 inch reach?

why wont they move up? do they have glass jaws??

i mean i know they have to be having hard time keeping weight down..

Answer 1

their size gives them an advantage at a lower weight class, plus they get more experience and exposure before turning heavyweight

Answer 2

They're just really heavyweights who didn't drink enough milk.