I don't use filters for protection unless there is an obvious hazard, and I would count crowds as a hazard, but street photography doesn't always involve crowds. I use a filter when I want to filter the light for photographic reasons.
I use a lens shade most of the time (the exceptions being lenses for which I don't have a practical shade option). A lens shade not only prevents extraneous light from falling on the elements, but also restricts the image circle of the lens to reduce veiling flare from internal reflections within the lens. Most flare is not caused by extraneous light but by the subject itself. It is always a good idea to use a proper shade, and it is worth considering whether the manufacturer's shade is really sufficient to maximally shade the lens. Shades can often be improved by adding black flocking paper to the inside of the shade.
I use a lens shade most of the time (the exceptions being lenses for which I don't have a practical shade option). A lens shade not only prevents extraneous light from falling on the elements, but also restricts the image circle of the lens to reduce veiling flare from internal reflections within the lens. Most flare is not caused by extraneous light but by the subject itself. It is always a good idea to use a proper shade, and it is worth considering whether the manufacturer's shade is really sufficient to maximally shade the lens. Shades can often be improved by adding black flocking paper to the inside of the shade.