But now - thanks to China's rapidly expanding economy and the introduction of Western values in cities and even parts of the rural countryside - things have changed.
They showcase a youthful spirit and a sweet smile.
The two-minute clip begins with an instructor - dressed in a smart black suit and white shirt - telling the vice girls that social media, such as Chinese Twitter, is not only the best way to market themselves to 'rich clients' but also to siphon off 'losers'.