What you're missing from this observation is that exercise doesn't extend one's lifetime that much, but just improves the general quality of life, meaning that

What you're missing from this observation is that exercise doesn't extend one's lifetime that much, but just improves the general quality of life, meaning that 80-year olds that are/were active in moderation now enjoy a bit better QOL [1]. [1] https://academic.oup.com/biomedgerontology/article/56/suppl_2/89/581109 https://academic.oup.com/biomedgerontology/article/56/suppl_...