Campaigns have personalities that affect how you can treat the account.
E-commerce Campaigns but built as Lead Generation.
Some potential reasons are you are in a competitive industry, you have other key phrases that have proven to convert, there's low search volume, and where you are searching (Google) from.
In some instances, yes. But the pros far outweigh the cons. Here are some reasons why you want to run branded campaign projects and how it can get you to the top SERP spot.