Mention difference

README.md

@@ -63,6 +63,8 @@ registry.register_factory(Database, create_database)
 
 The generator-based setup and cleanup may remind you of [Pytest fixtures](https://docs.pytest.org/en/stable/explanation/fixtures.html).
 
+Unlike typical dependency injection that passes your dependencies as arguments, the active obtainment of resources by calling `get()` when you *know* you're going to need it avoids the conundrum of either having to pass a factory (e.g., a connection pool -- which also puts the onus of cleanup on you), or eagerly creating resources that are never used.
+
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