Following the debate of whether coffee is good or bad for you can be like watching a ping-pong game. One day it is a super food, the next day it is linked to various diseases. The problem is the usual one - media inflating the importance of observational studies that can't really prove anything.
But here's some good news for lovers of the uplifting beverage: a new umbrella review of 127 meta-analyses finds that coffee is likely to be beneficial for most people.
There is some speculative discussion about potential reasons why coffee appears to have positive effects, like antioxidants. But the truth is that we don't know, it's all mostly just speculation.
Personally I believe coffee mostly appears good because it tends to replace other, less healthy, drinks. And also, coffee increases satiety, making people less likely to snack on unhealthy things.
This is my best guess: Coffee is not really good for you in itself. It just helps you avoid eating and drinking unhealthy things, that are always pretty much always available in today's society. But sure, I'm speculating too.