This is the thing that I get so mad at people about. There are some people who just *can't* be vegetarian. For one if you don't have cheese or eggs or some such you have to supplement B12 and for whatever reason there are people out there who every now and again just really need to eat meat. And that's just human biology. There's nothing bad about it. Frankly, I think vegetarians trying to shame people who just biologically can't do it are practicing a form of ableism.
Additionally though, vegetarianism and especially veganism is expensive. Leafy greens don't cost that much but the minute you start adding in beans, and supplements, and meat substitutes and vegetable proteins and everything else you need to round out a healthy vegetarian diet it gets prohibitive. I've had a few stints where I only had about $20 for my weekly groceries and it's just not possible to maintain a healthy vegetarian diet on that.