Not sure what the deal is but boy oh boy do Chinese people in Beijing and Hohhot love to spit! I do not know how many times (probably 50 plus) over the 11 days that I was in the country I heard the hacking, grinding, slurping sounds associated with the pre-spit moment, followed by the wonderful sound of release and impact. I would wake up in the early morning to the sound of these creative moments, often at 4am or 5am. Spitting seemed common amongst both men and women, indoors, outdoors it made no difference.
I was told the reason it was done was to clean out the mouth but damn!! what a disgusting habit.
You got to love going to a nice restaurant and seeing the NO SPITTING signs, nothing makes food more appetizing.