This vegan/vegetarian hype came up around the 60s, there were several studies made that showed that a vegan/vegetarian diet brought a vast improvement in the life span and health. Unfortunatly all these studies were invalid and unpresentative by scientific standarts, they just took let's say 1000 veetarians and 1000 meat eaters and researched their state of health. What's wrong with that you miht think, they did not consider the lifestyle beyond the diet as important. They just took the vegetarians and meat eaters, but if you look at the ways of life of the most vegetarians then you notice that the vast majority of them cares about their health, they do doctor checkups, work out regulary and pay attention to their diet, in short people that are concerned with their well being and state of health. But on the other hand the group of meat eaters was just the rest, the most of them were just people that don't care for the diet or their health, since it is the higher proportion of people obviosly the meat eaters that work out, go to checkups, look after their diet were outnumbered and couldn'T affect the study. Newer controlled studies have shown that a clean meat diet>vegan/vegetarian diet.
There's no logical reasons to become a vegetarian, only personal.