The patch-free week is to give your body a break from the hormones so that you can have a period. Also, if you are taking bcp or using a patch to regulate your period, that would be another reason for having a patch free week.
Some doctors suggest that you skip the four week of inert pills, or in your case, patch-free, and just go on to the first week of the next cycle's pills or patches. I *would not* do this without first talking to your doctor. In some people's opinion, mine included, this increase your risk for the negative side effects of birth control pills/patches. Do not do this unless your doctor is aware you are doing it, incase anything happens.