Others answered the main reason, but sometimes I find myself using "PRC" to indicate a particular government (~1950-Present) which unlike "China" excludes past dynasties, and is less-likely to be interpreted as referring to the people or culture.
For example, the potential differences between:
"France has always been X."
"The French republic has always been X."
"The French monarchy has always been X."
For example, the potential differences between: