Trackbacks - what good are they for SPAMmers?

I'm checking emails and deleting SPAM and grumbling about the amount of trackback SPAM that is showing up on my blogs on my main website. It has me thinking that I need to learn more about trackbacks, what exactly good do they do to the SPAMmers? Does it help improve traffic for them? Is it worth the time to delete it from my website blog or should I just ignore it (it is published as drafts that I have to approve before anyone else can see it).

I guess that is my next step, to learn about trackbacks and why they are getting my post about my dad's magnesium deficiency over 40 trackback spams a day. ::shaking head::