If it's a BACKUP wallet, why the hell was it on the server anyway? Backup is supposed to be offline and only manual transfer when funds in the active pool get lower than 50%ish. That should be the most ever stolen +- a few % from like really recent deposits and such.
Because it's easy and people are gullible.
No real life information posted on sites, anonymous money, plenty of suckers. Why would anyone not collect and bail? As long as there is no consequences people will continue to cheat/scam/hack their way through anything. It applies to any other place too, people will push the boundries as much as they can.
Same applies to the *coins themselves, one made success, look at all the imitators. Now look at mybitcoin, here's the successors to that story. I don't entirely believe it was hacked either.
Why does this keep happening? 
Because it's easy and people are gullible.
No real life information posted on sites, anonymous money, plenty of suckers. Why would anyone not collect and bail? As long as there is no consequences people will continue to cheat/scam/hack their way through anything. It applies to any other place too, people will push the boundries as much as they can.
Same applies to the *coins themselves, one made success, look at all the imitators. Now look at mybitcoin, here's the successors to that story. I don't entirely believe it was hacked either.