Well, I'm not sure that is the perception that many people have when making a loan. If you give a loan for $1000 with 10% interest, you expect to get $1100 after a (long) period of time, not to get $1000 + a $100 voucher worth of goods and services. I'm not saying that we shouldn't go back to the "voucher" system when money are backed by good and services, maybe that would be one of the fixes ...
In reality, I do not want those $1000 principle and $100 back quickly, I want borrower to pay very little principle and interest $100 to me every year, so that I can spend those $100 as I wish, and the borrower will work to earn back that $100 I spend, and pay back interest to me next year, etc...
In this way, the actual interest income will be more than $1000 for a long term loan, but there will never be $2000 existed at any given moment in the system