It doesn't have to, you fucking nitwit. Chemotherapy is for the benefit of the cancer patient.

And guess what? Everyone benefits from living in a society where everyone is able to access the medical care that they need.

Only someone truly insane, out-of-touch, malicious, misanthropic, cynical, selfish, and short-sighted would ever ask a question like "But how do I or anyone else benefit from you receiving medical treatment?"