Curing people is still profitable. If you are competing with an incumbent who only treats symptoms you can claim their business by curing patients.
Unless somehow it were possible to gain a monopoly on curing people, which is plausible but fundamentally not the responsibility of the researchers.
Have you heard of patents? For-profit pharmaceutical companies use them to establish a monopoly on drugs they develop.
Patents last 20 years, humanity existed for thousands. We can wait 100 more years for cures if it's the optimal way
The drug companies have a solution to patent limits called "evergreening" where once a patent is about to expire they make a very slight modification to the formula, pump massive amounts of cash into marketing it as "new and better" even when there are little to no benefits over the old formula. Doctors are easily bribed or mislead into prescribing the expensive new formula over generics and drug companies can continue to make large profits on old drugs instead of innovating.