The idea of a warning is not because anyone thinks you're going to read it and get scared and stop doing the thing you're hooked on.
The idea of a warning label is so your ice-age brain, the brain that loves to make up stories to explain things, has something to connect with when you start having a negative experience on something like social media, or something to help you realize that the thing, whatever it may be, is addictive and the reason you're having problems is because of that addictive quality. We greatly overestimate our brains and our capacity to properly identify threats and tell ourselves the correct story to escape the threat.