The choice to try and look younger is partly a function of inherent vanity and partly a function of pragmatic value. Appearing more youthful improves outcomes

The choice to try and look younger is partly a function of inherent vanity and partly a function of pragmatic value. Appearing more youthful improves outcomes in romance, socialization, and at work in both overt and subtle ways. The reason for this is quite simple: humans are wired to subconsciously respond positively to things (and especially people) that are visually appealing. This latter motivation is what drives my thinking on the subject and the implications are perhaps even more consequential for people in the tech industry. Tech is a realm that preferences youth and (sadly) will likely continue to do so. I had an epiphany some time ago when I encountered a 40 year old who looked about 25. What was striking was that people interacted with him AS IF he was 25. That demonstrated how surprisingly easy it is to short circuit the neural programming for assessing age (i.e. it seems predominantly visual). I should also note that sunscreen isn't some fountain of youth. There are various factors that contribute to the presentation of visual age and the use of sunscreen. For example: loss of skin elasticity due to a slowdown in collagen production with increasing age. And to address your last question: using sunscreen and maintaining a healthy lifestyle are not in any way mutually exclusive.