Isolated people tend to ignore their health in general. Married couples will have a 2nd person who will encourage them to take care of themselves and get things checked.

https://www.webmd.com/a-to-z-guides/news/20191010/marriage-tied-to-longer-life-span-new-data-shows

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7452000/