It's all about torque (weights, arms, and moments). Think about a teeter-totter at a playground. Put a 50 pound kid on the end and a 200 pound guy 1/4 of the way from the datum on the opposite side. The teeter-totter balances, but would you want to add four times the weight to do the same job? In other words, keep the arm long and the weight low to get the balance you want.