People grew up under harder conditions, boys often went out to work labor and farm jobs at age 10 or younger. There were way more me trying to be boxers, so pool was bigger. A seperate factor, due to lak of money they fought more often, but, sparred way less. Many just sparred lightly, since they fought so often.
old time group photos are the proof , hard to spot any overweight people . now days dont get me started everyones overweight even fit blokes