Well, there's a myriad of factors for why someone would do something like this and invest stock into it.
For one, it does work, but it's hellish on the metabolism and the brain. It's also mind-numbingly simple.
I have the kind of body and metabolism that needs to be pushed into ketosis to make good, forward progress with my physique. For instance, I'm dieting right now. Before my massive re-feed yesterday, I was a few pounds lighter than in my avi. With still using carb cycling and more macros than something like the Palumbo diet, I've continued to make progress. Unfortunately, my body being the way it is, I'm going to be switching to Dave's Keto for the last 4-6 weeks.
Not everyone needs it, undoubtedly. It's really become a little taboo in the industry (to a certain point) and people tend to find ways to work around resorting to ketosis if they can avoid it.