This is also due to the genocidal one child policy. Where famillies were forced to abort their unborn babies by authorities which led to tens or even hundreds of millions of babies been killed off this past 4 decades. So parents who wanted to have a male child only had one chance to get it right, so if the first child was determined to be a girl, they will kill off/abort the child before she was born and try again for a boy in future. This led to a situation where China now has tens of millions more men than women. So these men need wives/girlfriends as well. They can't live their while life without a partner . Reason human trafficking is rampant in China and even affects neighbouring countries where women from neighbouring countries (Vietnam, Cambodia, Laos, Thailand , Myanmar, North Korea etc are trafficked to China for money. Where there is demand , the market will.always look for ways to meet that demand. So this will continue.