Why doesn’t The Onion accept any outside writers?
Because they are an group of old friends who have considerable talent and have no need to accept outside submissions. In fact they will not even read submissions, they immediately trash all such mail, so that they will not be accusing of plaigarizing future stories.
UnuMondo
Do you know of any other other periodicals that trash submissions so that they will not be accused of plagiarizing stories? I don’t.
Plenty.
Lots of major magazines, mostly the big ones, won’t touch an unsolicited submission. It’s for the reasons already cited, i.e, they don’t need submissions and if they look at it the author can start whining that they stole his work or his idea.
Check out the Writer’s Market guide for writers.