That's a good point. And it's also the reason why treating symptoms is more popular than treating the root cause among Pharma companies. However, I think it will be a long time before cancer is eradicated, and so, there will be a need for cancer drugs for decades to come. Eventually, though, cancer will be eliminated, and then, along with that paradigm shift, there will be other health issues to pursue.
We don't even know what they will be, but they will also be in all likelihood lucrative because of the gatekeeper system, assuming the gatekeeper system remains the same. Interesting to muse about