What's the Point of Critical Hits?

https://www.youtube.com/watch?v=fMFkd7edBR0

critical-hits mechanics balance

Critical hits are deceptively simple: add more damage randomly. You can change both aspects (when to crit, and what to crit) to create unique mechanics, such as extra status effects, skill-based critical hits or even negative critical hits. Critical hits work well in some genres (RPGs, first-person shooters), but can frustrate in others (fighting or tactical games).