It has a side benefit of being a subtle intelligence signal if you're the "what about" person, i.e. "I saw the gap/flaw that OP missed, therefore smarter".
This, I think, is an "I'm smart" feedback loop that promotes more of the same behavior. It's a powerful motivator when you're on sites and boards also populated by ostensibly smart people. No one wants to be the dumb one. So you start to get wrapped up in being the bug finder/doubt-conjurer/"what about"-er.
Enough time goes by with those types being uncorrected and you wind up with comment sections that just turn into TTFC (time to first complaint) races, often by people with no practical experience in a domain save a quick wikipedia search or who don't even read tfa but boy howdy they've sure got some thoughts about that field as a "science" and gosh i can't wait to read them.
Of course this is all just an old man grumbling out a theory on a Tuesday. I'm not sure how to fully solve it and doubt there's a general solution. For myself, I was eventually broken of shitty habits like that through what would probably now be considered bullying. Gotta say though; sometimes it works. Sometimes your brain needs its ass kicked into realizing you're a smart cookie but you're not the smartest, and that's okay.
In my field, Civil Engineering, I get paid mostly to figure out all those things that could go wrong and mitigate or account for them within the budget and constraints available.
Experience is valued in engineering because you can see the probable future on things are likely to break/fail/go wrong, BEFORE they actually do.
It's not surprising to me then that a bunch of engineers who spend all day thinking in this way do the same in different contexts where it may be less appropriate because they are less knowledgeable.
I don't think it's necessarily a way to try to look smart or something.
Bingo! On HN, the "I am very smart" often becomes "I can reason about any unfamiliar ${complex field} from first principles in the time it takes to write a 2-paragraph comment based on only TFA". Such comments elicit confirmation bias from other non-experts and you may have a completely wrong (or not even wrong) comment at the top. It's a frustrating failure-mode of HN.
I'm more of a standing desk one right now.
In my experience, it is because most things are not good enough or are unacceptable. You see this in software engineering, technology, and science. Not in this particular case necessarily, but most "innovations" can be shown to be impractical and not good enough through back of the envelope calculations. Yet, the discourse on the Internet is full of these useless things, including this stupidity I remember back at the height of Covid: https://news.sky.com/story/coronavirus-lg-unveils-battery-po...