The "cheery," frequently alluded to by David Benatar in Better Never to Have Been, might be defined as those people experiencing optimistic bias, who are as a result untroubled by, or overly dismissive of, serious problems involving human suffering. Cheeriness is an extremely common trait, and the cheery certainly make up a majority of the human population and exert a major influence on social policy.
The fundamental problem with cheeriness is the assumption that a good life - a pleasant life - is relatively easy to achieve. This assumption is, of course, true for the cheery, but the cheery are able to ignore - and perhaps can't even conceive of - the suffering of a significant minority of the population. A good life is not easily achieved for many of us.
The cheery do not need to use extraordinary means to achieve a tolerable life. Behaviors that others engage in, perhaps in pursuit of a tolerable life - weird sex with lots of people, say, or using steroids or marijuana or LSD or benzodiazepines - strike the cheery as unnecessary and harmful. And, for a cheery person, these behaviors are wholly unnecessary - life is perfectly tolerable without them. And they increase the risk of harm! Who wants harm?
What the cheery cannot imagine is the importance, the function of these behaviors, and others like them - the pursuit of the interesting, and the temporary suspension of the intolerability of existence, which intolerability (for many) the cheery do not even perceive, and therefore do not properly weight as a problem.
I suspect that the same cheery social policy is at work with the question of suicide. Groundless faith that anyone can have a good life, bar none, leads to a general policy of suicide prohibition. A more mature understanding of the seriousness of suffering, and a more realistic evaluation of the possibility for its amelioration, would lead at least to a policy with more exceptions.