How did the word 'Beauty!' come to be a common exclamation of approval or satisfaction?

The earliest theory of beauty can be found in the works of ancient Greek philosophers from the pre-Socratic period, such as Pythagoras. The extant writings attributed to Pythagoras reveal that the Pythagorean school, if not Pythagoras himself, saw a strong connection between mathematics and beauty. In particular, they noted that objects proportioned according to the golden ratio seemed more attractive. Some modern research seems to confirm this, in that people whose facial features are symmetric and proportioned according the golden ratio are consistently ranked as more attractive than those whose faces are not.

According to an ancient Indian definition, the beautiful is that which from moment to moment is always new. That is to say, it removes the mind from the world in which things grow old. But considering that the visual system allows us to see by extracting the stable, rather than changing, features of the environment on a momentary basis, this ancient definition seems hard to support.

Different cultures have deified beauty, typically in female forms. Here is a list of the goddesses of beauty in four different mythologies.

Aphrodite - Greek mythology
Freya - Norse Mythology
Lakshmi - Hindu mythology
Venus - Roman mythology

Beauty contests claim to be able to judge beauty. The millihelen is sometimes jokingly defined as the scientific unit of human beauty. This derives from the legend of Helen of Troy as presented in Christopher Marlowe's The Tragical History of Doctor Faustus, in which her beauty was said to have launched a thousand ships. The millihelen is therefore the degree of beauty that can launch one ship.

The foundations laid by Greek and Roman artists set the standard for male beauty in western civilization. The ideal Roman is the more masculine form of pure male beauty. He is ideally defined (similarly to today's classic male beauty) as: larger (over 6 feet tall), far more muscular, long-legged, with a full head of thick hair, a high and wide forehead - a sign of intelligence – wide-set eyes, a strong browline, a strong perfect nose and profile, a smaller mouth, and a strong jaw line. This combination of factors would, as it does today, produce an impressive "grand" look of pure handsome masculinity.

Genetic Beauty
In the 1990 study by Langlois & Roggmann it was found that an extremely average face was considered the most attractive by the study group. A composite face (one of both sexes) was generated by combining all of the most common features from a group of photographs. The result was a face devoid of any irregularities, and especially asymetrical features. It was suggested that the features represented may indicate a lack of genetic variation, promoting an indication of a particularly desirable mate. Interestingly, in the same study, combining racial features from ethnic groups in creating a meta-average composite face produced much the same results.

There are three basic contributors to genetic beauty: averageness, symmetry, and sexual dimorphism. Averageness is sexually preferable because it potentially reflects stability during development, heterozygosity, and functional optimization. Bilateral symmetry is sexually preferable because it potentially reflects the ability to respond reliably to environmental pressures. Sexual dimorphism is sexually preferable because it indicates sexual maturity, reproductive potential, and health. Males tend to prefer a feminized face in females, while females' preference varies depending on the phase of their menstrual cycle.

Effects of beauty in human society
A survey conducted by London Guildhall University of 11,000 people showed that (subjectively) good-looking people earn more. Less attractive people earned, on average, 13% less than more attractive people, while the penalty for overweight was around 5%.

The term "beautiful people" is used to refer to those who closely follow trends in fashion, physical appearance, food, dining, wine, automobiles, and real estate, often at a considerable financial cost. Such people often mirror in appearance and consumer choices the characteristics and purchases of wealthy actors and actresses, models, or other celebrities. The term "beautiful people" originally referred to the musicians, actors and celebrities of the Californian "Flower Power" generation of the 1960s. The Beatles reference the original "beautiful people" in their 1967 song "Baby You're a Rich Man" on the Magical Mystery Tour album. With the close of the 1960s, the concept of beautiful people gradually came to encompass fashionistas and the "hip" people of New York City, expanding to its modern definition. Beautiful people usually enjoy an image-based and/or financially-based prestige which enhances their aura of success, power, and beauty.

http://en.wikipedia.org/wiki/Beauty#Theories_of_beauty

'Cause there are people who decided to make that be the way it is... and other people who continued to make that the way it is...