Eating better works. Eating less also works. If better isn't an option - and it's not, for many people - you're kind of stuck with less. Or you can go with a mixed approach - add in some better foods, eat less of the unhealthy ones, and cut out the very worst.
It doesn't help very much to tell someone what they should/shouldn't be eating when they don't have access to that sort of diet, either because of cost, physical access, cultural expectations, or parental/spousal control of their diet. It's also important to be aware that a lot of people have trouble sticking to diets that are extremely different from what they're used to. Eating a healthy vegetarian diet (let alone vegan) is a lot of work, requires a lot of thought, and involves a lot of unfamiliar foods with tastes and textures that may take time to adjust to (or just plain be intolerable for some of us).
Insisting that a perfectly healthy meat-, alcohol-, and sugar-free diet is the minimal necessary starting point for weight loss just gives people an excuse not to try other strategies if, for whatever reason, that diet won't work for them. The truth is there are a ton of ways to lose weight, and not all of them involve dietary perfection.
