I've only bought the pan a week ago and used it three times. Hot dogs, eggs, and steak.
When I'm done I clean it with a scrubby sponge and once with a little bit of detergent, then put it on the stove to dry quickly. Then while it's hot I smear maybe a teaspoon of vegetable oil on it with a paper towel "brush".
In between uses it's wet with oil, as you can see in the picture. How much residual oil should there be? I had the impression that it would be dryer.
Also, how much should I scrub? I am not going to leave crust of beef on there, but I also don't think it's supposed to be scrubbed back to new smoothness.
Technically you're correct, however, the unevenness of the cast iron pans is harder to clean and thus effectively retains more flavor. In common parlance: the pan absorbs flavor even though the iron doesn't (let's gloss over the few things that do bond to iron).
Beyond cast iron, which is cast and thus has a rough surface from the molding. Carbon steel pans are made from sheets and then shaped, it's the same material, only different processing. But the sheet is smooth, meaning less nooks and crannies for stuff to hide behind come cleaning time.
Also, have you considered the feel of grass against your fingers, I hear it's lovely this time of year.