Bitcoin thefts are this high because it is so dead easy to steal Bitcoins. You can literally exploit security breaches or holes in the software to steal the coins. Also you can fool people into sending you their coins -> in an irreversible manner, which makes things even worse!
People can steal fiat electronically in similar or analogous ways.
And don't forget that they can also steal it physicaly like in form of wallet or directly at your bank by changing the control panel into one modified with keylogger, belive me i've seen this.