Investments are different, because they have risk factored in.
Discussion
Comes down to the time value of money. Under fiat banks seek to add a component of interest to cover the inflation, the rest is the real interest rate that banks charge for the time value and risk of loss.
So banks will work under a Bitcoin system, simply not charging interest to cover inflation, comparably the interest rate would be lower all else equal.
No bank will lend someone who is not willing to repay or does not have the capacity to repay. So a blatant loan to say an unemployed individual for consumption is not going to happen. No one in their right mind would lend us Cb a person their hard earned Bitcoin.