I think some of it comes from short term thinking- if panda paradise is round the corner along with perfect bodies why treat your health with any respect. Likewise I think many including were told they wouldn't get old/sick and die so aren't emotionally prepared for it. Every sign of ageing reinforces the disappointment of no Armageddon.
I also think the very sedentary lifestyle as sport is discouraged or even having hobbies together with poor diet from low wages and not enough time have contributed. There is also a deep distrust of both medical and mental health professionals replaced by use of quack cures.