Then I would suggest that your impression is incorrect. Bavaria and Wurttemberg were both given new territory as Napoleon's allies, and their rulers were 'promoted' to the rank of king, as was the Saxon monarch. And Napoleon generally left their internal affairs alone. And those states chose Napoleon instead of Prussia and Austria, because the latter two wanted to ingest them and extinguish them as independent states. Baden and Hesse-Darmstadt also chose Napoleon over the larger German states for the same reasons.
Westphalia was an experiment and was a new state constructed by Napoleon, as was Berg. Those states needed years of peace to be allowed to consolidate and improve, as well as develop a national identity. Napoleon treated Westphalia quite different from Bavaria, Wurttemberg, Baden, Saxony, and Hesse-Darmstadt-quite differently which Owen Connelly illustrates quite well.