LLMs hallucinate because training on source material is a lossy process and bigger, heavier LLM-integrated systems that can research and cite primary sources are slow and expensive so few people use those techniques by default. Lowest time to a good enough response is the primary metric.
Journalists oversimplify and fail to ask followup questions because while they can research and cite primary sources, its slow and expensive in an infinitesimally short news cycle so nobody does that by default. Whoever publishes something that someone will click on first gets the ad impressions so thats the primary metric.
In either case, we've got pretty decent tools and techniques for better accuracy and education - whether via humans or LLMs and co - but most people, most of the time don't value them.