"Moreover, if some members of society reject to use new anti-aging technologies for some religious or any other reasons (inconvenience, non-compliance, fear of

"Moreover, if some members of society reject to use new anti-aging technologies for some religious or any other reasons (inconvenience, non-compliance, fear of side effects, costs, etc.), then the total population size may even decrease over time." I don't understand how this would decrease the population. Also why would they even bring this point up in the abstract. I thought this study was supposed to analyze the worst case scenario. Additionally an increase of 22% is not a trivial number when the population of the world is 7 billion.