All of the questions raised here are addressed here:
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https://www.fcc.gov/consumers/guides...ane-broadcasts
Notice I said 'addressed' rather than answered.
I knew before clicking this thread that the quick easy answer is "FCC rules", that have always stated you can't say certain words on regular network tv. I would assume it's a family values issue, where a lot of people out there (not us, obviously) simply do not want to hear a bunch of swearing in every program they try and watch.
Canada has it's FCC equivalent the Canadian Broadcast Standards Council:
CBSC Codes Canadian Broadcast Standards Council
Similar (but not exactly the same) rules here for most radio and regular tv networks (global, CBC, CTV)
Thank the gods for HBO/showtime/MovieCentral