FR tries to remain profanity free.
A couple reasons for using the "substitutions".
Some corporations and locations will screen out sites that are classified as "mature". This includes lunchtime surfing and any student who might want to search news articles using FR keywords, links to earlier articles, etc.
Also whereas FReepers can find other colorful words to use (like bullzogby or clymer), sometimes an article is posted to FR that uses foul language.
A good optional explanation... i.e. pi$$, a$$, f***...
I guess there is some logic to lame gambits other than non creative lazyness.. I stand down on being pi$$ed off.. that means I'm sitting you know.. d;-'