BJJ was developed by a man named Hélio Gracie back in the 30s in Brazil. He is famous for, amongst other things, openly challenging anyone from any background to fight him with no rules.
Over the years, Gracie refined the sport based on these street fights until he created one of the best unarmed forms of self-defense ever conceived.
While you should always do everything in your power to avoid actual fights, BJJ will give you a much better chance of emerging alive.
For one thing, you don’t need to strike, so there’s far less a chance that you’ll break your hand and end up with a serious disadvantage.
You can also debilitate your opponent without doing critical damage that could put you in trouble with the law.
The list goes on and on, but sufficed to say, should you ever find yourself needing to employ self-defense tactics, BJJ is excellent