> Why can't people simply publish negative results?

Mainly because it's not as interesting. For every positive result researchers find there are dozens of things they test that just don't work.

Imagine if the first test of "romantic priming" didn't work. Would the researchers really bother trying to publish "Hypothesised romantic priming effect was just a wild hunch after all."? And would the journal accept it? No way.

Of course if you get a negative effect for an established "fact", as in this case it can be published. But you have to be really really sure otherwise the reviewers will just say you did your experiment wrong.