Yes, because moving workflows is much more involved.  At the same time a campaign is pretty small configuration and very specific to production.  For example, while testing a campaign, you will likely not have all the dates setup like you want for production.  You will likely not have the same recurrence configurations, because you want to test at a different pace than you want in productions, etc.  So revision manage your business logic and digital assets, but the execution model (campaign) can be easily re-created.