It is a hard diet to do though. I found that eating out was very tricky, and that shopping at the grocery store was also challenging. It required meal planning, and just thinking of most food in the grocery store as non-edible.
There are good documentaries, books, etc. on why sugar is so bad for us. I really enjoyed the documentary ["Fed Up"](http://fedupmovie.com).
Extreme diets (i.e., 'eliminate X completely') tend to fail because they're hard to sustain.
In the absolute sense, you're absolutely right. But in my experience sugar tends to stoke a desire for more, in which case the form calories take is a crucial factor for success.
(Caveats: I know what works for me but couldn't tell you how much of the effects of eating sugar are physiological vs. emotional, etc.)
[EDIT: Typo]
However, I fell off due to emotional reasons. Personally, I have to be in a 100% sound frame of mind to stick to it - there's just so many carbs everywhere, it's easy to fall off.
But alcohol, it's hard. I like a beer or few to relax after work, but I think for me it became a habit. Cutting out alcohol at home was a neat compromise (allowing myself to indulge the couple of times a month I go out for programming group meetups) felt a bit like what I imagine giving up smoking would be like. It took me a couple of weeks to get used to not having a drink in my hand in the evening, and I didn't like it at all. Compounded by the fact that I don't drink soda, and rarely fruit juice (mostly water, coffee or tea).
However taking it a day at a time I did cut it out, and I became noticeably healthier. I started going to bed at a regular time, I felt more alert in the mornings. I think my work improved, I felt healthier in general, I lost weight and I felt like I had more energy.
I've 100% relapsed over Christmas, but I'm going to pick it up again in the new year.
The difference, for me, is that instead of prohibiting food - and thus, obsessing over what I can't have - I simply did specific goals and kept them up.
You can do the same thing with vegetables: To eat enough, you generally have to cut out other things, so the end result is a bonus. Sometimes it is hard at first, since you don't "like" certain things. This can be overcome with exposure and familiarity for many things, and expanded upon later on, even on things that failed previously.
Once you start looking at foods in this way - in terms of proteins, other nutrients (vegetables), and filler (carbs and fats) - it's easy to target foods high in protein and nutrients, and low in filler. This doesn't mean avoiding junk foods, but it gives you an excuse to not eat pizza crust, and means you'd target thin crust, or even opt for chicken strips.
My go-to for when I find myself eating out while on these diets (whole 30 and keto) is burgers with no bun, extra lettuce and other vegetables, and every sauce on the side.
The only thing that makes these diets work for me personally is that I have one of those tech jobs with free lunch every day and there are decent options. If I had to pre-plan and pack a lunch every day, it would be a lot harder. To my knowledge, nearly nobody (outside of tech) gets free, good-quality lunch supplied at work.
And even though I'm vegetarian and accustomed to being the weird one as far as food as concerned, not eating any sugar in any form really is exceptionally isolating. Any diet will have you feeling left out, but man. Sugar is a bitch.