Beautiful teeth are a sign of health and youth. It gives a person self confidence and a willingness to smile more often which reflects positively on first impressions.
Just as bad breath is a nuisance and can affect ones self confidence, so do teeth that are yellow, malaligned and stained.
This is not only true socially but generally goes hand-in-hand with oral health. Proper alignment and correctly contoured teeth not only look beautiful but can naturally contribute to less food and bacterial entrapment between teeth leading to lower number of cavities (which are caused by bacteria) as well as less bad breath.
This is why general and cosmetic dentistry is an integral part of ones goals to reduce bad breath.