A couple of years ago, we discovered that AT&T geoblocks all VOIP traffic from India. We sent some configured phones to them, because the bosses were told by AT&T that it would work fine. Nope. All the tracert results clearly showed them dropping the traffic. But then a few months ago, it started working! The India team emailed me asking to change out the names/extensions, and since then we've had no problems.

Yet another...

I can't access my State of Utah Retirment: https://www.urs.org/

I use it in pfsense router. It works against script kiddies, bots/botnets, at least partially. It's just another layer of security. And like it was mentioned before, it reduces log noise, with almost no effort.