It's like the guy who finds out you write for a living, and tells you he's been meaning to write a book as soon as he finds the time. It's a great story, and if you write it, he'll split the money with you.
There's a point where when people either realize it really is real work, or they think it's just something anyone can do--which is sort of what the Dire Straits song is about right? "That ain't working, that's the way to do, money for nothing and your chicks for free."
Only it's not like that. It's work.
Speaking and being paid as an expert isn't something anyone can do. You don't just put out a shingle saying "pay me to talk."
Reading slush is not something anyone can do. Slush is not something a publisher will pay you to read as a full-time job. Yes, editors take turns reading slush, along with interns and editorial assistants, and sometimes, hapless friends and relations of the editors when there's a desperate need for a slush kill.
No one can read slush for long. And the skill set for reading slush and spotting a diamond or a sapphire or even a piece of jasper in the rough is not something that's terribly common, either. It's actually a talent that's usually honed with years of experience working for an editor.