It's been said before, but facebook is wondering to keep tabs on people you used to kno, but haven't seen in a long time. Of course close friends, which you might not be able to speak in person, but also former classmates/teachers/...
You can see who gets married, what they'r doing in their jobs and casually ask them things.
Besides that, you have a range of groups that can provide you some intel on updates and such. For example, I can see from certain webcomics when a ne page is added or if they do a special somewhere. I know longer need to check their page every day to see if it's updated yet. Also in TV series, they use it to promote things or link to press articles, which might be interesting. Furthermore, among friends also press articles are spread and put up for discussion.
The apps and games are simple time killers. I do know that constant spamming of messages is annoying, but you can simply ignore them.