> A service has constant administration costs which are paid by the service provider. A properly designed library instead moves these costs to the users of the library.

What really happens is that users pay money to some service provider that has said administration costs and margins for providing said library as a service. Users don't want costs related to maintaining a library or infrastructure that it needs to provide its service to them. That's why things like AWS and Azure exist.

Unless of course SaaS providers are your "users" in this case ...