I always put it like this. If modern medicine did what it said on the tin, there wouldn't be "alternative medicine". The "closer to the truth" answer here isn't Scott's obviously cornpone opinion here, but this:

80% of medicine (mainstream or otherwise) is straight-up useless; this is because when it comes to conning the gullible & desperate, it's first-come, first-served. 80% of the other 20% will do nothing more than restore function or otherwise improve quality of life, rather than extend it. It's that tiny bit of remainder that will actually cause meaningful life extension, and these are the things that literally cost pennies.

E.G. what's important is not whiz-bang vaccines, but proper sanitation, NSAIDs, sterioids and the like. For a fraction of the cost, you get the majority of the benefit.

In short, diminishing returns on investment. No medicine this century is that much of an improvement on the "bessemer converter" level where it has obvious, large impacts on life expectancy. The ones that actually are tend to be treated as a heretic like Gallileo, as it inevitably is so effective because it upends the traditional understanding of bodily function. As such you should have very little hope for groundbreaking medical work to come out of corporate, given their witch hunting zeal.