It depends on one's wishes and financial status. If one feels that he has enough money to live a comfortable life after retirement, he can retire early. Not everyone has the same financial status and backup. Again if working Someone can establish a successful business but he should not have a problem to retire from his job. Many people live only by their job and in their case, early retirement will be like a kind of curse.
I agree with you, some people choose to retire early when they're financially stable while some wait till they are being told is time, in some situation some people delay their retirement age like pushing it forward instead of following the main date to retire, everyone has his or her reasons. Where you said "early retirement will be like a kind of curse" I don't feel it is, some people retire early base on health issues or family issues too. Some of us work just to use that monthly pay to sustain ourselves while we wait for our investment to settle before thinking of retiring why because many don't like working under anyone even the government.