Most of their training data says that Biden is president, because it was created/scraped pre-2025. AI models have no concept of temporal context when training on a source.

People use "who's the president?" as a cutoff check (sort of like paramedics do when triaging a potential head injury patient!), so they put it into the prompt. If people switched to asking who the CEO of Costco is, maybe they'd put that in the prompt too.