The biggest challenge any marketing campaign would have is how to convert the target audience to actual consumers.
Most Ads are geared to get you to buy only once. While the first sale is important, it does not necessarily of itself convert your target to consumers of your brand/product/service.
Most will buy from you once, but will not interact with you again. The thing that actually keeps your service afloat is the repeat buyers, those “converts” who already have a consumption habit.
Conversion for most products is only gained through consumer interaction. Unless your product is deemed as a necessity by the consumer, then you will be hard pressed to create a consumption habit.