You’re verging into conspiracy territory a little too much here. Truth is, there are good economic reasons to cure a disease or cancer: because the cure can be priced according to its (great) value.

Quick examples include:

* Hepatitis C - can now be cured in ~95% of cases. When the various drugs were released, they made many billions for the manufacturers, as the economic case for their use was clear.

* previously-untreated DLBCL (a type of lymphoma) - can be cured in ~2/3rds of patients, and many trials are ongoing (and have been run previously) to try to push this percentage higher. A treatment adding extra cures would be valued highly.