I'd never suggest it as a replacement for veggies, but some of the better formulated ones lately tend to contain various pre and probiotics, digestive enzymes, and some of the particular "greens" like Spirulina have benefits even if you eat plenty of veggies.Greens, Vegan, and Fruity cereal flavored everything. I appreciate the folks in this industry that are actually innovative and not just following the masses.
With that said, I cannot fathom someone needing a greens supp. I mean a serving is an equivalent to like 1 cup of broccoli. Are you eating hot dogs, fish sticks, and spaghetti-o's for your meals that you need a greens supp?
So I seem them as a decent health add on, but with that said lots still seem rather expensive and under dosed for these ingredients and maybe better off targeting those individually depending on need.
I think the Vegan options are great though. I don't really use them, but for some that option can really help. I am all for helpful things even if I can't benefit.