Shackleford and Larsen (1997) found people with symmetrical faces are rates as more attractive as this is an honest signal of genetic fitness.
People are also attracted to faces with neotenous features such as widely separated and large eyes because these trigger a protective or caring instinct which is a valuable resource for women wanting to reproduce.
McNulty(2008) suggested physical attractiveness remains important. He found evidence that initial attractiveness continues to be an important feature of the relationship after marriage.
Physical attractiveness may also matter because we have preconceived ideas about the personality traits an attractive person must have, they are almost universally positive. Dion(1972) 'what is beautiful is good'.
Dion found that physically attractive people found that physically attractive people are consistently rated as kind, strong, sociable and successful compared to unattractive people. This makes them more attractive to us so we behave positively towards them.
Halo effect describes how physical attractiveness tends to have a disproportionate influence on our judgements of another person's attributes.
Although we find physical attractiveness desirable, common sense tells us we cant all form relationships with the most attractive people. Our assessment of our own attractiveness plays a role in choice of romantic partner.
Walster (1966) suggested the matching hypothesis which states that people choose romantic partners who are roughly of similar attractiveness.
Our choice of partner is essentially a compromise, we desire the most physically attractive partners for evolutionary, social and cultural reasons but we balance this against the wish to avoid rejection. There is a difference in what we would like and what we are prepared to settle for.