`partition` has several arities. Removing coll from `(partition n step pad coll)` to create a transducer arity would collide with `(partition n step coll)`. Maybe the transducer could be `(partition n step)`, but it would need to be distinguished at run-time from `(partition n coll)`. In sum, `partition` is already wickedly complicated, introducing a transducer in the usual way would affect an existing arity, and if you're in shape to use a transducer anyway you can figure out how to get the job done with `partition-all`. ?