That isn’t what the sales pitch has been for the last 13 years, with lots of fanciful rhetoric about removing the need for banks (“you can be your own bank!” is basically a cliché by now).
> If I choose to self-custody, it's much safer to memorize a seed phrase than to store cash in my mattress.
Are you sure about this? Lots of people have been phished or compromised, whereas someone breaking in and searching your house is relatively uncommon and limited to people in the same area whereas your cryptocurrency can be stolen by anyone in the world.