For many transgender women who were unable to have access to puberty blockers, having a deep voice causes gender dysphoria. Unfortunately, taking estrogen does not cause your voice to stop being deep. Once a voice has dropped, it cannot be undropped (at least, not with hormones). Surgery to make the voice more feminine, or voice training are the only options for those who seek the gender euphoria of a more feminine voice.

Cleveland Clinic - Voice Feminization Surgery
Healthline - Everything You Need to Know About Voice Feminization Surgery
John Hopkins Medicine - Transgender and Gender-Diverse Voice Care
Mayo Clinic - Gender-affirming (transgender) voice therapy and surgery
Voice Doctor - Feminization laryngoplasty
Wikipedia - Feminization Laryngoplasty