I just like talking to people online, without actually having to know them or using a real name.. just like in the old internet times.
And the fact that 4chan is about the most free speech site on the net. Nothing here gets censored, verbally. You can say something and people WILL read it. There's no favoritism like in traditional image boards because there are no real user names, and there's no "downvoting" like in Reddit. My post matters as much as yours.
Then there's the fact that along with the things mentioned above, there's also a board for pretty much every interest here. So it makes it pretty damn comfy.
Keeping this shithole alive is worth $20 a year, definitely.