Yeah I wanted to say the same about these superzoom cameras. Largely one spends time in the wider end of things (0-100 mm equiv) so the rest of the 900 mills (equiv) are left pretty much unused.I think the answer(s) to your question may have been touched on already, however some of what's being discussed is more related to telephoto street photography than using a superzoom per se. Perspective and angle are big reasons why telephoto lenses are not liked for street. But for what is specific to superzooms, I think slow apertures, sluggish power zoom response and a lens that extends a ways out from the camera are the reasons why I personally don't like superzooms. That cannon barrel sticking out of superzoom bodies is pretty suspicious looking in my opinion. Small primes are a lot less intrusive on the street. Also wider lenses look less like you are aiming the camera directly at people that you want to get in the frame than telephoto or long barreled superzoom lenses.
Then there's the sensor noise thing as street photography is not always best done in the midday light.
Then there's the power zoom ugliness (ugh).