Granted loans are being distributed as debt and the amount of that debt is expressed with the quantity on paper bills or banking accounts.
So, why not expressing the quantity of the granted loans to some block chain units?
Regarding your example. A 3D printer printing tangible items called “bitcoins” every 10 minutes means that the items exist and thus, we can use quantity on some medium to express their amount. But in the current bitcoin scheme you only have quantity on the digital medium but not the items themselves. Neither tangible nor intangible. The items are fictional and as such they are called "bitcoins".
I think you're making it more complicated than it should. In the above part of your reply, you're trying to convince me that an asset has to exist and be tangible, but who told you that Bitcoin is an asset? It's a protocol, a set of rules in which computers follow to achieve this censorship resistant and double-spending deterrent electronic payment system.
In a payment system, units are required. Satoshi chose to call them bitcoins. (S)He didn't create value out of thin air. Whoever wanted a payment system that followed this consensus scheme could join and be part of its distributed ledger.
It's nothing, but a ledger of debts.