That's why they're spammers. Either they don't know how or won't spend the time to learn. Spamming is easy for them and they get paid to do it.
Kninjanin, I am basically just here to greet you, say hello and always so glad to see you -- because I don't know much about the spammers, I just let my ISP filter 'em out!
The furniture movers and porn hustlers from Bangalore can't be bothered with such things.