Many turnstiles can be jumped over. In this case it’s more about preventing theft and espionage.

I knew someone years and years ago who worked as an assistant to lawyers. The firm had a second office in the state capital, turns out someone was walking in and stealing laptops. I think they had done it three times the last I had heard.

Lawyer laptops going missing is a problem. I don’t know how they ended up fixing that.

It doesn't effectively stop it, but it forces them to give up some element of surprise. They have to either start the attack or start a trespassing action that will initiate contact with police.