It's necessary, because we're running out of space. The last blocks of the 4.3 billion IP addresses enabled by the current Internet Protocol -- IPv4 -- were assigned in February 2011. Asia Pacific has already run out of room. Europe will run out this year. The U.S. will run out next year. Et cetera.
The Internet of Things depends on it. IPv6 provides more than 340 trillion, trillion, trillion addresses -- "an essentially unlimited number," the Internet Society reassures -- which matters when every connected home appliance and street corner will need an IP address, nevermind the billions of people still not online.
This "holiday" had to happen. We've long-known we were going to run out of addresses, but few were willing to make the first move. The best way to accomplish that? Have the most influential players do it at the same time.