It's like using vast amount of information to create a self driving car vs. actually letting the car run on real roads. The first can only tell if it approximates reasonable driving, the second can tell if it avoids getting into dangerous situations. You can collect a lot of information on the US economy, but in the real world the FED is actively trying to manage things and you can remove that factor from the data.
Physicists's for example can't change the age of the universe they are operating in. It's a rather large unknown, but not exactly an unknown unkown.
At the other end, people trust surveys of eating habits. I don't care if you send out a billion of those things it's still bad data in systematic and changing ways.
In between, most animal studies in mice are looking at disease analog X, in a population of fat, minimally stimulated, etc.
But it turns out that it's worth applying the scientific method to these fields, so what you're left with are tough choices. To deal with these problems the way we would in a physics experiment would be prohibitively expensive, in the literal sense of prohibitive. You have to come to terms with the fact that you can only afford to get enough data that there's a non-negligible possibility of being misled. It's worth doing science here, and we can, but it's just plain hard. I didn't appreciate that before I started having to deal with it. Don't blame the subject for some practitioners' failings.