You can 100% emulate Websockets in Flash if you wanted, essentially librarys like socket.io use a flash fallback that does that. If you do a flash only game/app you probably just avoid the websocket overhead for faster development and better bandwith.

Raw sockets pass through firewalls and proxies exactly as good as websockets.

Not on corporate/school/etc networks they don't.

And avoiding WS and using normal sockets, god no. So much code for error handling and parsing and so on. Message passing is much nicer.