This enable you to split up your "investment" to several loan and minimize your risk therefore if someone defaulted the loan, you are not suffering from providing 100 % of it.
While it is true that I can split up my investment among multiple loans, my ultimate goal is to make profit that is a % on top of what I have given to someone. In case, say 3 out of 10 do not repay my loan and the remaining 7 do, in the best case scenario I will have the same amount of coins than what I began with. Hence, what is the point of investing? Had I left my coins in my wallet, I would be at the same point without the risk of losing.
This risk is unfortunately in every investment business, however in this case it is more expressed. I can only see that my money will be used to "buy more hardware for mining" or similar, but I am often not given additional details and expected profit. Some borrowers do, which indicates they are more serious, whereas others give only vague description of what they do with the money.