If you are the first to come up with a cure for that disease you will make huge profit compare to the rest of the industry. Especially if the cure involves coming up with a vaccine or a personalized treatment. Thats like the sustainable subscription wet dream of software companies.
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.