In the past 20 years with the growth of ISPs, telecom, internet infrastructure stuff, a huge percentage of it runs entirely from giant -48VDC battery banks, rectifiers, bus bars, fuse panels and distribution systems. In general as you get to the size of really big important core routers, DWDM systems and such, a lot of them don't even exist in AC powered versions.
The difference is that it's normal 3-phase AC power distributed to the building, and turned into DC within it.
The origin of this is within the Bell system and other similar legacy telco equipment manufacturers (Northern Telecom, etc), all of which standardized on -48VDC power systems more than 65 years ago.
It is just not apparent to most people how common and widespread -48VDC stuff is, since unless you work at the OSI layer 1 in the telecom business, you'll rarely have a reason to lay eyes on it in person.