Dumping that will cause massive downward price pressure, reducing the total effective value. See Musk's bitcoin dump earlier this year.

Inactive addresses with large balances are watched closely. Coins moved from those are going to be noticed and followed. It will be very hard to extract meaningful value without compromising your identity. Legal authorities may not agree that your possession of a particular string of digits entitles you to the proceeds.

People follow the path of least resistance - there is much to be made via malware and scams. Soft targets are plentiful, why make life harder on yourself while also taking on greater risk?