Eagle wingspans isn't something I've seen used, but the football fields unit does make sense when talking about something which is relatively long (can be measu

Eagle wingspans isn't something I've seen used, but the football fields unit does make sense when talking about something which is relatively long (can be measured in 1/2 to 3x the length of such a field). If you tell the average (US) person 1000 feet, they won't be able to envision it. But if you say "a little more than three football fields", they can visualize that. The point of strange units of measure is just to make a quantity relatable.