Because many people on social media are not here to experience a new perspective, they are here to lecture everyone else on how the world really works.
The reason for the bait replies are they want to be able to deliver the gotcha talking point they have heard somewhere else.
Why are people like this, mommy?
Often it is because the people involved have been shut down trying to lecture those around them on the same topics in real life but they still want to do it. They are not looking for conversation, they are looking for an audience to lecture at.
And why is daddy always drinking the unhappy juice?
Serious reply. Many people use alcohol to mask anxiety, especially men in societies that still hold on to the "Man must be stoic and strong at all times" horseshit.
Anxiety focused inward often manifests as depression.
Anxiety focused outward often manifests as aggression.