Because it's hard to prove. And, therefore, disprove.

It's intangible, and unquantifiable, so fuckwits who say "Just be confident, bro!" can't really be judged for giving bad advice if it doesn't work. There's no way the person offering that advice has to take responsibility for it.

Say, you hit the gym. You get fitter. "Cut" or "Swole" I believe are the terms the children are using these days. There's a visible, easily-proven results. You were scrawny or a lardarse; now you look like an East German female weightlifter.

Visible results, provable result, that can, on a general level, make you more attractive.

And if it doesn't work out for the guy, he can come back and say, listen, I look hot now, it didn't work like you bastards said it would.

Bam. Now the guys who told him to hit gym look like idiots.

The same with dress sense. "I stopped wearing my Mass Effect T-shirts and jorts everywhere, got some decent clothes, no women." Whoops. The guys who said dressing better would lead to more interest from women now look like idiots.

Or income. "Now earn six figures, no chicks." Shit. Don't the guys who said that look like liars?

But confidence? "Hey guys, I was really friendly and outgoing and witty, chicks don't dig it."

Now the onus is on the guy who got given the advice to "just be confident, stupid!" to prove that he's actually more confident. With fitness he can show off his body, with dress sense he can pose in his clothes, with money he can show his wealth via disposable wealth or pay stubs or where he lives, whatever.

Confidence? How to prove that? You can't prove that you were "more confident" this week than last week, especially on reddit, to those who weren't there.

It's like a never-ending vein of "good advice" people who like to be seen as giving "good advice" like to mine, as it's hard as fuck to prove wrong.