Earlier quoted context omitted.
Why 'generally'? Why can't crypto systems be designed to be more secure than other software given what is at stake (e.g. by making the effort to formally verify systems/applications). Not saying it will happen but don't see why it is impossible.
Because ultimately it all comes down to the security of your keys. Which are just information. Keeping keys secure is no different from keeping anything else secure. That's why 'generally'. And crypto doesn't do anything about key security. That's up to each person/org to figure out for themselves. (North Korea didn't hack the blockchain. They hacked however people/orgs kept their keys.)
This stuff is useful outside of blockchain as well.
The state of user protection in crypto right now is definitely bad, but there is a lot of work and research being done to improve it.
EDIT: I think I'm actually making the same point you made, but anyways here's a couple cool links and things to google for secret security :)