As a scientist I dislike the trend of observational studies getting massive press (see associations between Wine, Coffee, Chocolate etc and health/lifespan) because, as you say, we are doing (and should be funding more) studies on some of the underlying mechanisms but it is difficult to summarize them in a punchy headline.

There are have also been some really elegantly designes observational studies that use comparisons between family members, twins or features of the population to reduce bias in an ethical way.