Scientific notation is NOT the preferred method when writing large sums of money because it tends to distort the picture. Money is best understood using words like billions and trillions.
Science relies heavily on scientific notation as the minutest particles can be expressed without compromising the number itself. Extreme large numbers can also be expresed with some kind of perspective which would otherwise escape our understanding. Distances from the sun are so huge that there is a need to use scientific notation.
Imagine a scientist miscalculating because he misread a number or the positioning of the decimal point. It could be life-altering.
Statistics also relies on scientific notation as very small variances can be measured and then percentages obtained for insurance purposes or for other statistical reasons.
So scientific notation isn't only to record very large numbers or very small numbers but to allow their use conveniently and simply. Scientific calculators are also equipped to record numbers using scientific notation which prevents results from becoming distorted.
Scientific notation is useful in many ways.