That's because science journalism isn't very good. Cancer is never going to be cured, new cancer treatments just add to the laundry list of treatments that we can employ which increase survival rates incrementally over time. Cancer is a diverse group of illnesses that share some things in common, so a treatment for one isn't always going to be a treatment for another. Cancer is also often lifelong illness. We have no real good ways of removing all cancer from your body in many cases, and even if you appear to be "cured" it may very well come back at a later date.

This article's headline implies that this cancer was cured in 73% of study participants. If you actually look at the results of the study, about 70% had at least partial response, and about 30% of those that had a response had a complete response (meaning there is no evidence a tumor is still present). Additionally, this is only measuring short term responses (less than a year), and a later study will need to be published on long term response. So you have a treatment that we know short term leads to partial or complete remission most of the time. That doesn't generate as many clicks as "new treatment destroys bone cancer cells in 73% of patients" though.