Re: We didn't run out of ipv4
@stuart a /48 is bigger than a /64 in the same way that a /8 is bigger than a /16 in IPv4 :-)
The /64 is there to optimise routing, which means faster connections.
Ask yourself this - given any "normal" home network, does anyone actually need an IPv4 /24 netblock ? do you have >200 devices at home ?
The same logic applies in IPv6 - there are some spare addresses in your local subnet - so what ?
The benefit is that auto-configuration relies on this standard network length, your devices can auto-configure without having to worry about DHCP and the like, so its easier to set up.