Yes people are living longer. Yes if you live healthily you cut down the risk of certain illnesses. But many people still die relatively young and many elderly people have major illnesses.
So a third of men die before they are 65. And on a personal level, my incredibly fit and healthy looking aunt at 78 who still goes long long hill walks, had a heart bypass 7 years ago. My fit 84 year old neighbour had cancer in her 60's. And I know numerous people who lived very healthy lives and died in their 60's.
You may be lucky and live a long life with no major illness until near the end. Some people do. But please don't assume that is the norm, because it isn't.