I've never understood why water found in the wild should reach a temperature of about 200 to be safe, but food leftovers only need to reach 165 to be considered safe. Does someone know the reason for this difference?
What you're trying to kill in both cases is different.
When you're cooking meat, you're mostly trying to kill the organisms which infect meat: listeria, salmonella, trichinosis, roundworm, etc. All of these organisms die at 165F after a few minutes. Further, presumably you're buying government-inspected meat which has very few, if any, of these organisms to begin with. Were you, for some reason, eating "risky" meat, it would be a better idea to cook it to a higher temperature (or not eat it in the first place).
On the other hand, when you're purifying water, you're trying to kill not only organisms like e.coli and cholera (which die quickly at relatively low temperatures), but organisms like giardia and cryptosporidium, which can survive much higher temperatures for brief periods. While it's possible to kill them at 165F, you would need to hold the water at that temperature for more than 30 minutes. It's far easier to heat the water up to 190F or higher, which will kill organisms in less than a minute.
165F will kill many things and leave meat proteins very tasty. That is why it is the recommendation for meat.
Water doesn't burn when heated past 165F. And if heated to boiling (212F) not only will it kill more things faster but it is easier to tell when you get there. Who carries a thermometer with them when they go hiking?