They have lots of salt/fat, because unless it is a puree of some sort, or a vegetarian/vegan restaurants, (places with a chef that is attentive), veggies are treated as a side no one wants to eat and are usually tossed in the trash by the busing staff. Which is why you often see frozen, canned, or the lowest quality presented slathered in salt/fat: the real taste has been obliterated by processing.
The problem is they are trucked great distances so are harvested too early (since they are more robust when unripe). I've had local butter lettuce that tasted sweet and firm, and tomatoes and carrots that tasted like candy. But I'm lucky to live near a lot of local agriculture grown with intention (Portland).
It's a bummer that every city/town in the US doesn't have local produce of some sort.