In my case, I'm healthy. No past health problems. Height and weight for a 66 year old are within norms. Grandpa lived to 99 and dad to 92, both died in their sleep and nether had any health problems that prevented them from enjoying life.
On the wife's side, one grand mother lived to 93 and the other to 103. Her mother is still going strong. Wife had her female plumbing removed and bladder rehung.
So in our case working a few more years, delaying Social Security checks for a few more years will provide for a bigger retirement nest egg for us.
Your mileage will vary.