Why does everyone use scare tactics when advising about travel in Brasil?

I'm here now, its really not that dangerous as long as you keep ur head screwed on. scare tactics like -don't travel on the bus, don't go to Salvador, don't go to the football matches, so many more. Why not enjoy Brasil, its amazing, just take taxis at night, don't go off alone down quiet streets, keep vigilant and don't travel in fear, make the most of it!