Absolutely not. All cities have rougher areas, because cities need workers that are only paid enough to live in affordable hosing and affordable housing inevitably clumps together.
But it doesn't automatically follow that a rough area is "bad" in the way it is in San Francisco. Plenty of cities in Australia, for example, have their share of upmarket and downmarket suburbs. But the lesser suburbs are rarely dangerous and their poor reputation is largely socio-economic, relativistic and/or historical prejudice.
SF is weird in that one block can be pretty nice, and a walk a few minutes in the wrong direction can put you in the middle of skid row. It is a rapid and jarring transition.
A night out for the unaware can start with an early dinner at a Michelin-starred restaurant in Hayes. You enjoy a performance of La Boheme at the opera, and afterwards walk across the street to look at the beautiful neoclassical architecture of City Hall lit up at night with colors of pride. You walk one more block looking for a nightcap and... What the fuck, why am I surrounded by tents, drug dealers, and someone seizing on the sidewalk from a fentanyl overdose?
But it doesn't automatically follow that a rough area is "bad" in the way it is in San Francisco. Plenty of cities in Australia, for example, have their share of upmarket and downmarket suburbs. But the lesser suburbs are rarely dangerous and their poor reputation is largely socio-economic, relativistic and/or historical prejudice.