How would you go about doing this? As an example, if you loaned someone 167 monero to buy a car and expect them to pay you back in 7 years like a bank does you would be requesting 167xmr*6.02% (to counter xmr inflation) for a total of 177.053xmr. 177.053xmr/84 (months in 7 years) would be 2.107xmr a month. At the moment that is fine, but if the usd price of monero rises and the borrower is being paid in usd then they are going to default and you will loose the xmr. The only way I could see to counteract this would be to lower the Monero payments per month, but then that would take even longer to be repaid.
When gold was used as currency, it would be shaved off using a scale to confirm the weight (gold is a very soft metal, easily ‘sliced’ off the coin/bar. Shopkeepers had their own scales but wary customers could carry gold pocket scales to confirm the weight.
Just like you can spend fractions of a cryptocoin, you can spend fractions of a precious metal coin.