Because the reality of imperfect human nature doesn’t trouble them. They don’t want to change the impossible. The universe is not something they struggle with. It’s something to appreciate. They celebrate present goods over future fantasies. They struggle to improve their their family and career, not the lives of others. They break the problem of life into small pieces. Each family doing the yeoman’s labor of creating the smallest tribe possible:the family. And by creating a multitude of those successful small tribes, the greater tribe emerges from the sum of its parts, not the pursuit of an idealistic folly: an attempt to obtain universal homogenous belief in the pursuit of shared feelings, ideas, and goals. The progressive instead, runs on a squirrel cage, attempting to gain consensus from the multitude, never getting there, and feeling frustrated for having failed. Human nature is all but immutable. Our preferences are genetic. They are determined by the difference in mating strategy between the genders and the imprecision of the gender creation process caused by the difference in in-utero concentrations of hormones that enhance or diminish those gender-based emotional biases.
Conservatives are happier because they are more successful at life itself. No human can be happy when he struggles against the universe. It is an exercise in perpetual frustration.