Why haven't we cured cancer yet?

... Because the "smart" people work on Wall Street/for consulting firms.

... Because Facebook acquired Instagram.

We can't even "cure" a relatively simple virus like the cold or influenza, and cancer is like 10,000x times more complicated - gotta respect all the hackers who're working in the medical field...

TLDR: Breast cancers, for instance, have been shown to harbor at least 1,700 different mutations, but only three of them showed up in at least 10% of patients, with the great majority of them being unique to each patient. The most recent study in Nature discussed above shows that even a single subtype of breast cancer that is generally treated clinically more or less the same, TNBC, varies wildly (and almost continuously) in the genomic changes and mutations each tumor has. Not only that, but each TNBC is in essence several diseases, because each TNBC is made up of many different clones that have evolved as the tumor itself grew, progressed, and evolved. All of this occurs even before the tumor has been subjected to any treatment at all. As if that’s not bad enough, it would appear that tumors are a mosaic of groups of many different tumor cell types that develop through branching evolution such that metastases can be very different from the primary tumor and even different regions of the primary tumor can be very different from each other, so much so that finding a “favorable prognosis signature” on a core biopsy means only that that one area biopsied has that gene signature. Large areas elsewhere in the tumor could have the unfavorable prognosis signature.

And even more interesting if you look at the history of a tumor the mutations goes back for a fairly long time, possibly on the order of 30+ years. While it may not be an actual cure, removing abnormal cells early may be more effective than trying to treat cancer in the last 1-10% of it's lifetime when it's already become a diversified killing machine.