I think some people simply have a tremendous craving for meat. They like the taste and the texture and the mouth feel. I’ve been lucky and have been able to satisfy my need for those tastes and textures with other things, and therefore, I never crave meat, although I do have fond memories of certain things like carnitas, roast turkey and fried chicken, but I don’t crave them.
No one really needs to eat meat, to get all of the protein and vitamins and minerals, but you do have to be diligent about actually eating those things (and knowing where to find them, and having them readily available). Most people are not willing, nor do they have the time (and definitely not the interest) to become a vegetarian. And I pity the picky people of this world, because it’s very hard for them too, especially if they don’t like the taste of vegetables or have never heard of cardamom hee hee.
Some people, like my cousin who has celiac disease, and is a really picky eater, simply wouldn’t survive (at least not happily) without eating meat. She eats meat instead of vegetables and grains.
Also, in our society, being a vegetarian is still looked upon with a certain disdain. Our society is set up to cater to meat eaters, so even if one wanted to become a vegetarian, unless they have the mental stamina to put up with all of the negativity, and difficulty of finding healthy vegetarian options (Cheetos and Mountain Dew don’t count) it’s not likely that most people would do that, even if they knew that it was better for them in the long run.
So I guess need is a relative term.