Forcing end users to secure their wallet file in effect forces them to be techies to feel safe enough to use the currency.
A few years ago, this might have been true, but not anymore. Dropbox has millions of users. OS X comes standard with Time Machine. Backup is becoming easier and more common. There are also centralized Bitcoin services such as
MyBitcoin which manage your wallet for you. Just like other cloud services, they handle backups and presumably use infrastructure that's far more reliable than most home users have.
By the time Bitcoin is popular enough for viruses to steal wallets, these kind of services will be far more prevalent.