Security technologies can only get better over time. I would argue that with hardware wallets, recovery seed backups well-protected & well-stored, M-of-N signatures, etc, you can get to a level of security that's already far far better than cash, and good enough for 99.99% of use cases.
All of those require me to have air-tight opsec all of the time. One screw-up and you can be totally cleaned out with no remedy other than the courts (which can take years!)
In the real world, I lose my actual wallet every 5 years or so. Worst case, I lose $40 cash and have to spend a couple hours reporting credit cards stolen.
The best feature of a bank is that you can outsource all that opsec to them in exchange for a trust relationship with the bank. The latter is far easier to manage day-to-day.
