I really think email spam is a problem already solved (at least for most end users). I use gmail, yahoo and hotmail (for different accounts) and I rarely get any spam.
Now, I know the anti-spam tools are working very hard to stay updated, but using the spammers tactic is too much. Why change if the current research/defense tools are working?
I think the main reason is that Linux users are most likely not willing to pay for something like that, while Mac users are used to pay for everything..