Are there vacancies for social media professionals or is social media a part of a marketing professional's job?

Social media marketing professionals are high demand such as Facebook Ad Specialists or Pinterest Marketing Professionals.

Social Media is a specialization and in ideal situations has dedicated vacancies but aas @Jillian says it is subjected to the size and marketing outlook of the company too. I've seen this as specialized KRA's and more often than not included in the Digital Marketing KRA's and sometime even in the Marketing KRA too. 

I believe it depends on the size and type of company.