Sometimes we use probability distributions that are not exact representations of the physical processes that they are

Question:

Sometimes we use probability distributions that are not exact representations of the physical processes that they are meant to represent. (For example, we might use a normal for a of individuals’ weights, even though no one can weigh less than zero pounds.) Why do we do this?
Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...