Health insurance companies have profit margins of 2%, and owning their stock gives you a terrible return. Buybacks are just a tax efficient way of giving out dividends, which is expected of any business, and a large portion of health insurers are non profits.
This is all public information, there are 7 different publicly listed insurers to look up 10-Ks for and all the various Kaiser, Cambia, and other BCBS non profit orgs also have open financials.
However, pharmaceutical companies do have 20%+ profit margins, and do have phenomenal returns, and do do buybacks, since they can afford it. Next up is probably the software companies (Epic, etc), the legal firms, the hospitals, and the doctor groups.