Spammers - morons with email

I really don't understand the mentality of spammers. Why do they make their obnoxious messages so easy to detect? For example -
They send messages that have a subject line beginning RE: - now I know perfectly well what ongoing email correspondence I have so this marks them out as spam.
They misspell words like viagra in the hope, I assume, of fooling antispam software but the misspellings themselves signal the message as spam.
They put names in the subject line but other people's names - "check this out Raymond" so I know at once that this is spam.
I delete any message with FYI in the subject.
I delete any message selling meds - or should that be medz?
I delete any message that has apparently come from me (spammers fake much of the content of their message but why make it so blatent? I mean, burglars don't knock on your door and pretend to be you, do they? They might pretend to be someone else but to pretend to be the person they are talking to is so stupid it goes below zero on the moronicity scale and falls off the edge of the paper).

In short, they send out messages that betray themselves as rubbish even before I have bothered to read them, which of course I rarely do. What I do instead is to collect the silly names that the spammers give themselves though, and hope one day to write a book in which every character is named from a spam email. Who can be indifferent to people named Shemika Blankenship, Cletus Massey, Gaylord Grisham or Maredad Blanchard? And when they meet Chuck Camp, Wiley Ondrusek and Addie R. Bledsoe, I think a Booker prize is just a formality.