It’s not just kidney stones though (and I don’t know people who have had issues with that from keto)—you feel awful on keto (headaches, nausea, flu-like even) if you don’t amp up both water and electrolytes. This is especially true when beginning keto, as a side effect of glycogen metabolism. Here’s an explanation of it: https://www.perfectketo.com/keto-electrolytes/
Also it’s important to be clear that keto/ketosis is nothing like being in diabetic ketoacidosis. It’s at most producing very low amounts of ketones, nowhere near the amount in DKA. For some people this is an effective way of managing weight and blood sugars (esp for people in the prediabetes/early T2 phase). Personally, I’ve done it from time to time, and it’s the only time my blood sugars are ever a flatline consistently, and it’s been easy to lose weight and eat fewer calories without feeling hungry all the time. Definitely not for everyone, but it seems like some people are able to achieve results with it that they are simply not otherwise, which is why they do it.