Cryptocurrency prices fluctuate greatly, and since currencies are irreversible, you use a collateral token, and if the price of the token moves sharply downward, the collateral may be liquidated.
Or you can borrow from someone you know, or you can be lent based on confidence in your account. Here, any delay in paying the fees, or if the price rises sharply, will lead to negative confidence in your account, or at least make you pay higher costs than a regular loan.