Earlier quoted context omitted.
I think that they're running webserver on localhost and they are connecting to it from their website opened in browser, probably for some integration.
How is that going to work when most of the users are behind NAT/Firewalls? That's a connection model that just doesn't work well on the modern Internet. I'm also kind of baffled by the need to install a Blizzard root cert in the cert store. That's normally only necessary for people who are too cheap to get their certs signed (Blizzard makes enough money to do this) or who want to MitM encrypted traffic from your host…
I don't like this practice too and I would opt-out of that "feature" having the choice. I just used to develop similar software, so I understand why they did that.