Maybe because they are not constantly facing stupid advertisements telling them their worth depends on a youthful appearance; they are probably in good shape due to healthy diets and physical activity; they do not face the same pressure to perform by capitalism when their age starts to impact their abilities, though that probably happens at a higher age compared to us because of their shape; and they probably don’t know FOMO and don’t think about what could and what couldn’t be achieved in the years left, highlighted by companies who want to sell you stuff or vacations or services, if you are surrounded by ads all the time. Ads can be disastrous to mental health if you are receptive. Simple wellbeing is not a thing if it doesn’t cost you money, happiness is tight to consumption.