They may talk a good game and know how to get your listings live and looking nice, but do they know how to properly utilize all the available business features? How are they measuring results for you? Are they constantly searching for the next new strategy that will give you an edge? Can they tell a good idea from a bad one? And most importantly, is the person doing all this for you going to stay with you for 5 or 10 years? If they leave, what will you do?
There's a lot more to consider when hiring a social media professional for your business because there is a lot more on the line. Social media for business is a completely different animal than posting selfies and memes. Remember, everyone you meet can call themselves a "photographer" because they carry a nice camera in their pocket, but that alone is not a good reason to hire them to shoot your wedding.