Some seed investor puts a million pieces of money into a company, that company starts getting a lot of customers, new people are willing to pay much more for pieces of that company. But now this company has gone from zero to lots of value, and so that first investor can behave like they now have a billion pieces of money instead of the million they had originally (whether that's cashing out a small amount, or borrowing against it). So if the economy grows in a non-zero-sum way, how do you avoid inflation? The total value in the system (due to the circulation of money and the productive activity) goes up, and lots of it isn't in the form of "pieces of currency."
Is there so much difference between "lending money" - giving money on the belief that the counterparty will pay you back more over time - and "investing" - giving money on the belief that the share of the thing will be worth more over time? In the absence of regulations, even someone like a bank who's holding other people's deposits could do either sort of investment (and so is VC just a special sort of "bank")?