That's one of the many issues with expecting a collective resolution. Question is: why do people feel they need to be able to discuss issues way beyond their understanding and personal experience online with others who also don't know much about it? If actually done well, moderation is a full time job but nobody is interested in paying a bunch of online jannies to clean their space.
That's why I favor individual responsibility, and opting out of the possibility of being exposed to (or perpetuating) misinformation. Maybe in the future we can have forums for verified experts of a field, where regular people can have discussions with them and ask questions etc. But these would be moderated places where you do need to bring proof and sound arguments, not emotionally charged headlines.
The stories and information posted on social media are artistic works of fiction and falsehood. Only a fool would take anything posted as fact.
Reasons vary between people. It's not important. If you want to know, ask the people in question.
Don't think everyone SHOULD be doing it like you. If you feel like being upbeat, be upbeat. ACCEPT not everyone is but they don't get to force their view on you either.
It's naive to think one way is more "right" than the other.