Literal cash and similar assets are the only dead money in the economy.

Even low and zero interest savings accounts are used by banks to back loans.

So for example, when someone buys gold or bitcoin, they are isolating that money from the productive economy. When they buy a share of a business, they are participating in the financial backing of that business (they generally aren't actually directly contributing to the business, but the business can do some types of business against its value on the stock market).