What can/should be done about journals that spam potential contributors?
So what is, if anything, being done about this?


Ignore them.

No, you are not missing anything.  These journals are scams, not serious scientific literature.  

If you plan to publish a longer version of your conference paper, send it to one of the journals that your paper cites, or at least to a journal where you recognize a significant fraction of the editorial board.

Sadly, trying to "doing something about" these scammers is as futile as "doing something about" fake email quota warnings, diploma mills, exiled Nigerian princes, international email lotteries, and three-card monte.  Set up your mail program to blacklist their emails if you can, but then move on with your life.