Some of the benefits of hiring a wedding planner aren't on the usual list. One of the perks and advantages of hiring a wedding planner is that they aren't related to you.
They aren't your family or friends. They will give you an unbiased opinion about ideas. They aren't trying to please everyone in your family...just you, the bride. While they respect and value traditions, the won't try to convince you of something because "it's always been done that way." Having someone who isn't emotionally invested can be a life saver. We can step back and look at the big picture and find the compromise.
We can help negotiate through tricky situations. Dealing with family can sometimes be one of the hardest aspects of wedding planning. Navigating through these family issues with a neutral person can save your sanity and relationships.