These types of loans of course aren't useful for most people in the traditional sense where somebody needs access to money they don't have. These are mostly for 2 cases: 1) Exposure to other crypto when you think both your collatoral and the crpyto you want to be lent will both be worth more. SO you borrow $100 worth of USDC, give $200 BTC as collatoral, use the $100 USDC to buy $100 worth of ETH. SO if after a month ETH and BTC have gone up, you can sell enough to pay the $100 USDC loan and keep the profit.
2) Access to illiquid capital. If you have $1 million of BTC but don't want to sell it and trigger a capital gains event, you use that as temporary collateral to get access to something else, thus never selling your current crpyto holdings (unless they fall below the liquidate threshold of the loan)
I should say too, using these methods still has counter party risk regardless.