> If I lend my friend $10 every day for lunch and he pays me back the next day and this happens 5 days in a row in what context would it make sense to say I have lent him $50 dollars?

If I plan on bailing out his broke ass for the next 5 days, then I have to set aside $50 to do so regardless of whether or not he actually repays me on time. This is closer to the actual situation at hand.