There is an incentive to sell drugs for chronic conditions. Curing these conditions would cut into the profits for selling drugs for chronic conditions -- I hope it should be hard to misunderstood -- it is just a simple math (lifetime customer for chronic condition vs. a single purchase for the cure).
In practice that hardly works, due to nasty business practices and lobbying.
On the other hand this argument works better for scientific progress. Yes, company selling like insulin shots might not invest into curing diabetes. That does not mean that there is not plenty of researchers looking into that issue, potentially disrupting the market.
I just hate that this gets framed in a way that is just a step from conspiracy theories.