That's really incisive. Just as with rental housing, the responsibility for the maintenance gets shifted, not just the responsibility for building. It seems to me like software maintenance has gotten more and more important relative to software building over time... but it might just be an optical illusion. (I mean, Windows 3.1 didn't update itself overnight...) I wonder if this is true, and if so, what's driving it?

Yes, and you only organisationally learn this distinction really once you've been say, bitten hard by a contract renewal that completely up-ends your architecture, requiring huge efforts to stay in compliance with the new terms because by this point you're well and truly locked into the product.