You can't play off a good which is hard to move as "susceptible to theft" when you can log in and copy a data file and have succeeded in stealing a whole bunch of money.
Even nowadays with a few simple steps you can make your bitcoin stash VERY VERY secure. Install a fresh copy of linux on a USB, disconnect all networking capabilities, boot to the USB, create a new wallet/address (brain or paper) using established methodology, turn off computer, remove USB, presto, you have a un-hackable bitcoin address. You could even create a multi-sig stash that requires a digital signature from multiple people (2-of-3, 3-of-5, etc). Obviously, this is cumbersome and non-trival for the average joe. But with a small amount of imagination it is easy to see how everyday solutions could be developed.
You also haven't covered anything about backups, which means if you lose that USB or it dies, then poof all that money becomes unrecoverable permanently.
You can't even access that money now without booting an entire new OS on the computer, which means good luck spending it, not to mention, for a digital currency you might want network connectivity as well.
There are several tools that allow you to create a transaction offline (using similar steps to what I listed above, which only take 10-20 minutes) and then you can broadcast the raw transaction text to the network using something like http://blockchain.info/pushtx. Again, this only necessary for super secure storage of long term savings/investments/etc.
Lastly, one could easily keep small, day-to-day amounts on their smartphone, which can spent and transferred quite conveniently (average joe level convenient). Then top up this spending wallet every so often using your offline wallet (10 minute time commitment every week or two).
The options/methods for doing all of this will only get easier. We are in the pre-alpha stages of digital currency software right now. Think web in the early 90s.
Its websites coded by script kiddies such as inputs.io by an under 18 Australian who ignore security and then get hacked (or more likely do a runner with the coins themselves) once they get enough suckers to send them bitcoin
Bitcoins can be owned, so it's better to own them instead of storing them in someone's wallet on some website. Send you money to a shitty exchange nearby, buy bitcoins, move them into your own wallet immediately. Then you won't care if someone hacks the exchange.