Power failure are very frequent depending on where you live in the country, and it only takes a brief sag in voltage to take down your system/rack/entire data center if you are unprotected by a UPS.

A good, solid UPS is very reliable as long as you keep it maintained. The major issue is keeping the batteries good, not continually exposing them to deep discharges, etc.

There is a reason that the Microsofts, Googles and other huge users of data centers spend millions of dollars on critical infrastructure like UPSs in order to protect their investments.

The decision to roll the tech out in Washington DC may have been made since Sprint's Executive HQ is in Reston, VA. Reston is just a stones throw from DC in the Dulles Corridor, the facility is basically on the main highway between DC and Dulles International Airport; its a very short distance.