I feel like those, who are driven only by health benefits and don't educate themselves on other aspects, may eventually get back to eating animal products and in this case, veganism or plant-based lifestyle may be just a temporary fix or a phase. The thing is that veganism is not only about us, it's about shifting our focus from ourselves to other beings, who need more attention than we do. It's about reducing suffering of animals, about choosing products, which don't contribute to global warming and don't require usage of enormous amount of water to be produced. It's about compassion and love towards all beings.
Don't get me wrong, I am more than happy when someone decides to try plant-based diet even without being aware of other, more important, issues. Because ultimately it reduces demand for those products, which is what we strive for! It's important to remember that we tend to prioritize ourselves, our health, our well-being, our appearance. That's why it is crucial to make this lifestyle appealing, to convince people to try going plant-based, because after all health benefits are incredible! You can easily prevent many chronic diseases, increase energy level and become more positive, happy and vibrant.
The reason why some people go back to eating animal products is lack of education. Once you switch your diet to plant-based, you should learn more, gather informations, know why you are choosing to eliminate these products. Probably majority of people from your surrounding are not vegan, therefore it's easy to justify consuming meat, since everyone does that. That's why watching documentaries, reading books, articles, expanding your knowledge is so important. To understand, know your facts and reasons.
Veganism is not a diet, it's a lifestyle. The fact that it's became so popular and some treat it as a way to lose weight may bring confusion. However, I believe that it's a good thing as it rises awareness and reduces demand for animal products. Even if not everyone will stick to this lifestyle forever or not truly understand it. We should share our knowledge and lead by example.
Personally, I went vegan for health reasons. Then, I understood that animals are actually suffering (and that diary products are not cruelty free!) and how animal agriculture destroys our planet. If not for those reasons, I would probably got back to eating cheesecake and milk chocolate. Because of that I feel like education is the key, when it comes to staying on this lifestyle long term.
If you want to learn more, you can watch:
Forks over knives