Here's why:

* Lipids are a broad category of organic compounds that are characterized by their insolubility in water.

* Steroids are a type of lipid that have a specific four-ring structure.

* Sex hormones like estrogen, testosterone, and progesterone are all steroid hormones.

While sex hormones are technically lipids, it's more precise to say they are steroids because that classification highlights their unique structure and function.