I imagine people share these for 3 reasons.

1. People encounter information at different times. Sure you’ve seen the article but someone else hasn’t (although for popular topics, this likely become near zero quickly enough)
2. People want to signal to their group that they are in the group. Why do people share anything with their little opinions attached. In part it’s so that they can cement their place in their tribe. Democrats or republicans or anything else, you are supposed to be angry about the things that anger your tribe and happy about the things that please your tribe.
3. Anxiety. Our brains are sorta wired for “stress -> action -> relief” cycles. We survive because we encounter a stressor, take some action to address it, and are then relieved of that stressor. Feel hunger, eat food, feel better. The current world has many stressors that can’t be meaningfully impacted in an individual level. You can read an article about something that outrages you or highlights an injustice you believe is occurring, but then there is no action to take. So sharing becomes an effective action substitute. Did it solve anything? Nope, but your brain doesn’t care, it’s just happy you took some sort of action.

Brand that old uncool politicians go on tv and beg people to buy.

Good thing American consumers love desperation.