Because for every one of those examples a password recovery option is available. People use password recoveries all the time. There is no password recovery for an encrypted wallet. Encrypted wallets by default would be a disaster.
Worse many "casual" users may be confused by the very concept of irrecoverable password
. Since almost no services exist that have irrecoverable passwords casual users likely need an education.
I would imagine enabling encryption on the 1.0 client would need to be pretty comprehensive. Something more like a wizard explaining that losing password means a complete and irrecoverable loss of funds and that there is no "forgot password" option.
It would also be good to:
* compare the user's password against a known password list ("your attempted password is already known to attackers please try another one")
* give the user a password strength meter with practical strengths ("your password can be guessed in less than 4 days by an attacker with a single computer"
* providing a "print out page" for safe keeping (with warnings like store this in a safe, all your funds can be stolen is this document is lost)
It would also be a good idea to provide "popup" warnings with frequency and intrusiveness directly related to the balance.
Gavin is absolutely correct in pointing out Bitcoin is 0.x. It is 0.x for a reason.