Because that's the way enums work (http://docs.python.org/dev/library/enum):

>>> import socket
>>> list(socket.SocketType)
[<SocketType.SOCK_DGRAM: 2>, <SocketType.SOCK_SEQPACKET: 5>, <SocketType.SOCK_NONBLOCK: 2048>, <SocketType.SOCK_CLOEXEC: 524288>, <SocketType.SOCK_RDM: 4>, <SocketType.SOCK_STREAM: 1>, <SocketType.SOCK_RAW: 3>]
>>> list(socket.AddressFamily)
[<AddressFamily.AF_NETLINK: 16>, <AddressFamily.AF_CAN: 29>, <AddressFamily.AF_WANPIPE: 25>, <AddressFamily.AF_UNSPEC: 0>, <AddressFamily.AF_KEY: 15>, <AddressFamily.AF_PPPOX: 24>, <AddressFamily.AF_IPX: 4>, <AddressFamily.AF_UNIX: 1>, <AddressFamily.AF_IRDA: 23>, <AddressFamily.AF_SECURITY: 14>, <AddressFamily.AF_PACKET: 17>, <AddressFamily.AF_AX25: 3>, <AddressFamily.AF_APPLETALK: 5>, <AddressFamily.AF_NETROM: 6>, <AddressFamily.AF_ATMPVC: 8>, <AddressFamily.AF_SNA: 22>, <AddressFamily.AF_INET6: 10>, <AddressFamily.AF_TIPC: 30>, <AddressFamily.AF_RDS: 21>, <AddressFamily.AF_NETBEUI: 13>, <AddressFamily.AF_INET: 2>, <AddressFamily.AF_X25: 9>, <AddressFamily.AF_ECONET: 19>, <AddressFamily.AF_LLC: 26>, <AddressFamily.AF_ROSE: 11>, <AddressFamily.AF_BRIDGE: 7>, <AddressFamily.AF_ASH: 18>, <AddressFamily.AF_ATMSVC: 20>]

Marking as a docs issue, since the fact that these are now enums should be covered in the socket module docs.