The document discusses five main reasons that people leave their jobs: 1) company culture issues like an unclear mission or uncomfortable work environment; 2) feeling underappreciated and like they could be easily replaced; 3) lack of support needed to do their job well; 4) insufficient opportunities for advancement like learning new skills; and 5) compensation, though this is usually a lesser reason than the prior four issues. The document emphasizes that employers should prioritize addressing these reasons to improve employee retention.