Seriously...what is the purpose of spam?

I've been increasingly bombarded with spam here on Liberal Common Sense but what doesn't make any sense is it's being posted on older posts, some that are over two years old. I don't get it, is it some desperate attempt to build up links? It's not like anyone I know in their right mind is going to see something like the most recent piece of garbage I got hit with:

Very nice site! Arrow canada uniform blouses cat lover gifts license plate frames Casino bacarat Today show hair lose

And say HOLY MOTHER OF GOD! I was looking for a uniform blouse let me run my behind over right now to that spammer and buy something! Same with Glass City Jungle but over there the majority of the spam is people trying to push prescription drugs without having to have a prescription and most of that gets caught by my spam blocker. Like anyone would really buy a prescription drug from one of these people? Hell you'd be better off taking your chances on a downtown street corner...

I'm systemmatically going thru every single post when a spammer visits and deleting him and all of his little buddies that I might have missed from before and then closing comments on those older threads. Today alone it took over an hour but eventually...They'll have no place left to go....

:-)