Opportunity. I had planned on retiring at 60 since I was 50, but the mothership company (we were a subsidiary of) offered an early retirement for the first time in the company's over-century-long existence where they added years and service time if you parachuted out, and I jumped on that. Perfect timing. So I retired at 57 as if I was 61. The wife retired the year before I did. Retirement was calculated using your last highest 5 years' salary average over the last 10, age, and time in-service, so actually working a few more years wouldn't have added much to my retirement check anyway.
We have a fat nest egg stashed away due to years of 401k packing, and it's nice to know we don't really have to worry about money anymore. Being DINK (double income, no kids) was a big plus for us. No kids or grandkids bumming money all the time. Found out you can live on a whole lot less than what you think you can and still do ok. We'll probably need it though the older we get when Medicare and other health problems suck up a good portion of spare cash.
Could we have continued to work? Sure. But why? I haven't gotten to Social Security age yet but will soon. Wife just started hers, and it just all goes in the joint account. When we both are pulling money from SS, based on the estimates, we'll be bringing more home through pensions and SS than we did when we were working. Not even touching the 401k's. So we are still able to maintain the standard of living we were used to before, even with some pesky inflation. But still, nobody likes inflation.
And hopefully soon, we'll be able to get back to doing a bit more travelling that's been put on hold due to Covid.