The root cause is that humans have a powerful negativity bias. I once heard someone who'd been an editor at a major paper say that negative articles get as many as thousands of times more clicks than positive articles. It would be very hard for any media business not to prioritize negativity and conflict. They would not survive.
I've seen it myself. I once penned a very combative blog post about the usability flaws in IPv6. It got hundreds of times more hits than anything else I have ever written combined. The big difference seemed to be the negative, combative, snarky tone. If you write like a snarky narcissistic asshole, you get 10-100X the attention. (I ended up taking it down because I didn't like the tone after thinking about it for a while.)
This bias likely has an evolutionary root. "If you mistake a bush for a lion, you're fine. If you mistake a lion for a bush, you're dead." We came of age in an environment of scarcity, predation, and conflict, and are hard-wired to pay close attention to anything that even remotely smells like a threat or induces negative emotions.
I would even say the number of comments shows how controversial something is while the amount of likes shows how uncontroversial it is.
Comments take more effort than hitting a like. You want to add your 2c and before you know it, others want to address what you said, too. And you get endless repetitions of the same arguments buried deep in chats and threads.
Finally, there is nothing more addictive and compelling than the notification “Someone just replied to your comment”
Take away that and the tendency of people to want to show off how "verysmart" they are and you'd have to shut down HN.
This is the result of people wanting something for free. Which normally is like the opposite of capitalism.
Under capitalism, news agencies are privately owned, and have to pay employees. They compete for advertising and subscription revenue.
Thus, they are subject to market discipline and the market selects for clickbat outrage articles that are widely shared. When it comes to subscriptions, the for-profit news organizations cannot afford to tell both sides of the story. If FOX News hosts regularly admitted that progressives are decent people and single payer systems may have some good sides , they’d lose their audience. If Daily Kos said that conservatives have a point in this or the other thing, their readers would be frustrated/triggered and move elsewhere.
Facebook selects for more engagement and sends notifications because if they didn’t, then another network would become #1.
The point is... capitalism drives us into echo chambers and distracts/interrupts us at dinner. It is a tragedy of the commons where the commins is human attention and decency.
On the other hand, science, wikipedia and open source software do not have a profit motive. There is competition, yes — to be the first to contribute to the snowball of free information. This is actually collaboration. Our news can be done this way.
Look at https://rational.app to see what I’m talking about.
Journalism adapted to being disrupted by the Internet, by serving one sided audience with one sided outrage articles. The market selects for those. If FOX news admitted liberals weren’t that bad, they would lose much of their audience.
And social network algorithms select for “engagement” which once again prioritizes ones sided outrage clickbait.