Being a social media manager brings with it some key benefits within a freelance setting. The most recognizable being the fact that you are your own boss. You make the decisions and answer to no one.
You send the invoices and you set the policies. Heck, you could sit in your underpants all day on the computer if you wanted to.
The other is money. It is an in-demand role, but one that companies are still struggling to come to terms with.
Some companies realize and understand the value social media could bring to their enterprise and are willing to invest heavily in robust social media campaigns. Being your own boss, you can decide how to set your costs and price accordingly.
Another attractive reason is the low barriers to entry. With low start-up costs and plenty of online resources (like this one!) to rapidly decrease the learning curve, anyone can launch a freelance social management business within a short space of time.