Why do people have dogs fights

why do people have dog fights. Dog fighting has been recored since back in 1750's bit it really started in the 1860's manly in the Northwest. There's is different types of levels of dog fighting one is street fighting. This came up in alleys. What led to this was when people said my dog can kill yours. This might be associated with gang activity. The payoff is usually money,drugs, or bragging rights.