Because not everyone can afford or is able to drive.
I took this picture today around 4:30PM. This woman had to wait a very long time to cross. And she had to get right up to the edge of the wide non-pedestrian friendly curb in order to have time to cross when she finally did. The drivers trying to make the light turning right paid her no mind.
We are fortunate to live in a walkable village. We have things to walk and bike to and should be able to do so safely. We care that the village is safe for people outside of a car, because we want our kids to be able to be independent. And we want all residents and visitors, regardless of ability, to safely get around.