In Asia, it can seem almost mandatory. I don't think that's good. For example this happens in Japan, but IME there's much less drinking in China.

Depending on the nature of the employer, it may not be unreasonable to prohibit alcohol on site. Would you want workers to be drinking at a nuclear power plant even after they've finished work for the day? Also, it looks bad for pilots to be observed drinking at airport bars and doesn't inspire confidence in the safety standards of their airline. Many restaurants prohibit drinking on the premises not only because they feel that is leads to problems but also because of a concern that people might help themselves to the restaurant's alcohol without paying for it.