People may use breast forms for a variety of reasons. Here are some of the most common:

1. After mastectomy or breast surgery: Women who have undergone a mastectomy or other breast surgery may choose to use breast forms as a way to restore their body image and regain a sense of confidence. Breast forms can help to create the appearance of a natural breast and balance out the body's proportions.
2. For gender transition: Transgender women may use breast forms as part of their transition process, especially in the early stages of hormone therapy when breast growth is limited. Breast forms can help to create a more feminine silhouette and help with gender dysphoria.
3. To enhance their appearance: Some people with smaller breasts may choose to use breast forms as a cosmetic option to create the appearance of a larger chest. Breast forms can also be used as part of a costume or for other aesthetic reasons.
4. For medical reasons: Breast forms can be used as part of medical treatment for conditions such as Poland syndrome or amastia, which affect breast development. They can also be used to correct breast asymmetry.

Overall, breast forms can be an important tool for people looking to enhance their appearance, regain their confidence, or alleviate discomfort caused by medical conditions. It is important to choose high-quality breast forms that fit well and are comfortable to wear.