If you mail a torn banknote to the Treasury they will send you a brand new one. There is no recourse if a hard drive or electronic wallet containing a bunch of Bitcoin is destroyed, for example.

You can say "tough luck", sure, but the end result is that the amount of money circulating in the economy will be decreasing every day.

And how does a fork solve anything? You can't just say, hey throw away all your existing Bitcoin, we're starting from scratch and using this new one now.