First, it's factually false. There are now multiple Hepatitis C cures for a formerly chronic (and eventually fatal) disease, let alone all the other chronic conditions that pharmaceutical companies have cured or diminished. And "big pharma" companies have gotten to the same stage as these teams with antibiotics.
Second, it doesn't even make sense unless you treat "big pharma" as a single monolithic entity. In reality, it's many many companies, including startup pharmaceutical companies, all competing against each other. I don't think of bacterial infections generally as chronic conditions in the first place, but if one company makes money on a drug that manages some chronic bacterial infection, there's no reason that another company would be worried about taking away profits from the first company.