"I know a few women who are prescribed testosterone to increase libido but otherwise do not know other reasons why women choose to take this."

It’s understandable — many women don’t realize how important testosterone is throughout life. Both women and men naturally produce testosterone and estrogen, just in different amounts. For women, testosterone is a vital hormone that affects much more than libido.
One key example is bone health. Testosterone works with estrogen to build bone: it promotes new bone formation, while estrogen controls the breakdown of old bone. Together, they protect bones better than either hormone alone. Around 70% of women over 50 in the U.S. have either osteopenia or osteoporosis. That’s why forums like the Mayo Clinic osteoporosis boards are among the busiest — women are looking for guidance and support for a very common problem.
Testosterone also affects genitourinary and overall health. While declining estrogen drives most menopause-related symptoms like vaginal dryness and tissue thinning, low testosterone can make these issues worse. Beyond that, it supports muscle strength, energy, mood, and even cognitive function.
Besides libido, replacing low testosterone in women can support many aspects of health and quality of life that most women aren’t even aware of.

I have an estradiol and testosterone pellet, as well as progesterone and estradiol vaginal cream in my bhrt regime. I wanted it to have a healthy libido, help with building and maintaining muscle. In addition helping keep bones healthy. Also, because it is a hormone that both women and men have and is depleted with age why would you not have it as part of hormone replacement!