Steve's plot did if you think about it. It served, pretty much, to give a reason why the entire family (sans obviously Roger) would be angry at Stan. It also was another fine example of the "Steve gets a chance at a hot girl and gets screwed over" plot. The resolution was right there: he got screwed over. That's how it's supposed to end.
I liked it, although it was predictable. (who couldn't see Stan getting addicted to crack and refusing rehab?) I like the American Dad episodes that have twists a little more, but not bad. The crack commercial was hilarious as well as Francine ignoring Haley's cries for her "pot addiction"...