Although there are a few people who sometimes use a longer lens for Street Photography, there are far more that dismiss a longer focal length. The internet is filled with posts telling you to buy a 28mm, or a 35mm or at most a 50mm lens. Sure they are all good options (who doesn’t like a nifty 50) but it doesn’t have to be that way.
The fact I don’t have to stand so close to people is the one over arching thing that makes a longer length so great. When you’re just starting out, or still learning like I am, a 85mm length is great. Allowing you to get the up close and personal shots that make street photography so great, but not have to deal with the people that go with it.
Using my A7c and a 85mm prime is the perfect combination of nice and light with enough ability to capture the shots I really want and be a little more removed from the subjects. This may change with confidence and progression, but let it be said that you simply do not need to buy some expensive glass nor stand really close to people to get great shots. I love 85mm for almost everything, and you might too.