http://www.hormones.gr/211/article/article.html concerns Ancient Greece, so not primitive. But, I think you should be cautious about declaring primitive people as having their lives markedly shortened by waterborn pathogens; at least cautious enough to be able to cite some strong evidence?
I didn’t claim that people died in their 30s or that waterborne pathogens were a major cause of shortened life. The latter certainly seems plausible though. My point there was only that basing your water sanitation on the habits of primitive people is obviously misguided.
Typhoid fever is another really nasty disease, often contaminated water transmitted, that still kills hundreds of thousands of people per year (http://www.who.int/immunization/diseases/typhoid/en/). But in countries with clean water and good sanitation the infection rate is very little. As an exmaple: the US over time: https://www.wikidoc.org/images/3/30/Typhoid_stats.gif
I can't say how much this shortened the average lifespan overall, but these are some pretty significant diseases which are largely transmitted by contaminated water (or food), and which are largely eliminated by water and sanitation treatment systems. I'm sure there's some others, these are just the first two that came to mind.
Giardia by comparison is more of a "nuisance", but with treatment methods so cheap (I mean, iodine tablets are on the order .15 a tablet or so) I really don't see a reason to take the risk of that or other stomach-upsetting bugs getting in you.
Filter your backcountry water, people.