It's because there are very high penalties for carrying excess weight in aerospace, and the environment is uncontrolled. Imagine trying to calculate how much ga

It's because there are very high penalties for carrying excess weight in aerospace, and the environment is uncontrolled. Imagine trying to calculate how much gasoline you need to drive from A to B which is 1,000 miles away, but for every extra fluid ounce of fuel you have at the end, you have to pay $10,000. You have to deal with varying weather, wind speeds, traffic and so on. How would you do this "precisely"? Let's remind ourselves that this rocket did 99% of its mission successfully, but didn't seal the deal.