I use it to have a visual anchor of what the place looks like. While driving sometimes its not appropriate to slow down and read the building number, but a big visual like building color or shape will help. Especially if I want to enter the building where missing it means missing the destination.

Another use case of mine, is when I have to go through an intersection of streets or freeways with a lot of merging and diverging routes, I use street view to know which lanes do I have to be on to not miss my exits, or what signs would I read if I am on the correct route.

So in summary, large visual hints.