While it is probably true that the pressure of society contributes to the higher rate of suicides we see today, I believe their is a larger problem. I believe there is a softening of expectations and life experiences in general that do not prepare children and young adults for real pressures of life. Fore example in years past, team awards were not given to all participants and children had to experience wins and losses at a young age. Today, those tough lessons are learned far too late in life and many people haven't developed the skills to cope with loss and disappointment.
Yes, somehow suicides have become a part of our everyday life thanks to TV and newspapers. Today, it is normal that we hear a person have committed suicide, but it should be quite opposite. The TV and newspapers are doing something wrong, as though they are intentionally advertise such actions.
Opportunities for comparisons of others' lives is everywhere. We only see a part though, not the whole picture. So to view someone else's life and compare it to your own puts an unhealthy amount of pressure on a person. Communication is easier than ever today but we communicate so little. We have all of this outside pressure that marks us with depression and anxiety. This leads to more suicides.
It would make sense that no one in their tribe killed themselves because tribes tend to be very communal and community-based societies. There's less selfishness and less greed because they are not trying to do better than anyone. They are just trying to survive and make sure everyone is taken care of regardless of any factors that modern society has in place. They are generally more happy just because they have support, both emotional, physical and financial that one does not find out in modern society very often.
The suicide rate in Western cultures is about 1 per 10000 people. The population of this tribe is probably a few hundred, That's problem number one: visibility. Also, A suicide in those tribes would probably be done via falling down heights or poisoning, Both of which could be easily attributed to an accident without proper methods and tools of investigation.
So there might easily be suicides at the same rate as in Western cultures, They just wouldn't be as obvious as with Western media.