Dancing Masters were, and remain to this day, an essential component in the transmission of social dance.
'It had come to pass, that afternoon, that Miss Morleena Kenwigs had received an invitation to repair next day, per steamer from Westminster Bridge, unto the Eel-pie Island at Twickenham: there to make merry upon a cold collation, bottled beer, shrub, and shrimps, and to dance in the open air to the music of a locomotive band, conveyed thither for the purpose: the steamer being specially engaged by a dancing-master of extensive connection for the accommodation of his numerous pupils, and the pupils displaying their appreciation of the dancing-master's services, by purchasing themselves, and inducing their friends to do the like, divers light- blue tickets, entitling them to join the expedition. (Charles Dickens - Nicholas Nickleby)'
Modern day example
Dancing-Masters in Early Eighteenth-Century London - Moira Goff 
DANCE AND TEACHERS OF DANCE IN EIGHTEENTH-CENTURY BATH - Trevor Fawcett 
Here is an insightful article about the role of the Dancing Masters, from The Conversation website
Norfolk Dancing Masters  (Maggie Marsh 2007)