Do these idiots not have a cover on the well? Do they not boil water? Wouldn’t random lake water be just as teeming with harmful bacteria?
You can see that the well DOES have a cover in all of the images of it.
And there's no guarantee that boiling the water would have made it safe; that depends on whether the contaminants are micro-organisms like parasites and cysts, bacteria, viruses, or even just invisible, tasteless, and odorless like arsenic.
On top of all that, as many have already pointed out, boiling water is fuel-intensive and not something to be taken lightly. Like, sure, it has to be done to cook, but boiling all your water every time is going to use up a lot of fuel.
Yes, while lake water will have bacteria in it, whether that is the specific harmful bacteria, and in sufficient quantities to actually kill a person, depends on a number of variables. But if even insects are dying when they touch a well's water, I think that said well water is far more deadly than any random lake's water.