In the case of steem, a lot of people acquired the token by vesting an account and then voting other accounts thereby minting their own money so in other words, they become their own bank but rather than keep the tokens, they sell the tokens in their alt accounts they have built so they can make returns on their investment.

Let's not forget that it is also an open market when someone has a successful sell, it means there is someone somewhere who just had a successful buy.