And if Facebook knows what issues you care about and what parties/politicians you support, they can easily put all that together in order to sell political advertising campaigns targeting you to specific politicians and give them the specific issues to put in the campaign.
So really, this is about Facebook improving their product (you) for their advertisers (political buyers, in this case). Happy data collection. I'm sure Google and the other big advertising companies will follow suit if they can.
The fact they can get additional less informed voters (those who don't vote currently are on average less informed than those who do vote) to show up at elections (which will make the average voter knowledge lower) is just the bonus cherry on top of their advertising Sundae. But hey, as long as that gets them more advertising money to propagandize those less informed voters, it's all good, right?