In order to keep down comments about people's accept rates, accept rates are no longer displayed. However, that leads to a question: what is the incentive to accept answers now? Are we in a situation where there is no real incentive to accept answers?
Yes, you get +2 uncapped rep. But that's hardly a big incentive, is it? Without an incentive, why exactly should a user accept anything?
For the plurality of questions, the highest voted answer is the one that gets accepted. Sometimes this is because it is the accepted answer (people see it first and vote it up), and sometimes not. But in any case, my point is this: for the person asking the question, what benefit is there to accepting any particular answer?
If a user accepts an answer, then the question instantly becomes less popular. It's an immediate signal that the issue is closed to the satisfaction of the person asking the question. Obviously people can (and sometimes do) come along to provide useful answers to questions that have accepted answers. But by and large, if you're patroling SO for questions to answer, you don't look for questions with accepted answers.
This is good for the people who answer questions, as they don't waste time reading something that probably has a satisfactory answer. But at the same time, it's bad for the person asking the question. The question gets less views and fewer answers. If someone sees an question with 2 unaccepted answers, they might decide to take a look at it to see if there's something those two guys missed.
Given this, why would someone accept an answer on their questions? There's no real reason to do so, as it greatly decreases through traffic on the question.
Accepting answers is a very good thing for the site. People who choose not accept answers universally are subverting the whole point of the accept system. They benefit their questions to the detriment of the site as a whole.
If you think this is a phantasmal issue, consider this guy, who unaccepted every answer on his questions recently. This was seen by some as "rage unaccepting", but his answer seems to suggest that he simply doesn't want to accept answers, period. That he'll just upvote whatever he likes and that'll be the end of it. That he wants all his questions to be unaccepted, which is why he unaccepted even his own answers that he accepted.
So there is evidence of at least one person subverting the system.
If we want answers to be accepted, I think we need some kind of incentive. And the +2 rep isn't doing it. Noisy though the visible accept rate was, it did at least prevent this. Some have suggested a "citizenship level" that measures various features. This seems like a solution so long as it is publicly visible without having to go to someone's profile.