In addition to the security issues, they would have to deal with non-negligible transaction costs every time they wanted to convert it to actual money so that they could purchase something. If they were using it as an investment, they had to deal with the opportunity cost of underperforming $SPY.
It really comes down to the burglar's expectations. If most crypto holders used geographically separated multi-sig, these attacks wouldn't be worth the effort anymore.
It’s the same logic as iPhones bricking themselves after being stolen. Even if your specific phone isn't an iPhone, the fact that most phones are now useless to thieves discourages the crime across the board.
Our knowledge is constantly expanding, allowing us to build things differently than we used to. Modern cryptography, which makes things like multi-sig possible, is only a few decades old; it didn't even exist when the current banking industry was being established.
This isn’t just a problem in the Netherlands or a thing of the past. 2025 actually saw the highest number of attacks ever recorded [0].
There are ways to prevent this. Like using multi-sig with geographical separation (so you can't move funds alone) or setting up forced time-delays. Ultimately, being your own bank is a massive responsibility, and I think too many people take that reality too lightly.