Because lettuce is filler whose main purpose seems to be to take up space on the plate. It doesn't provide an saity, and something like iceburg lettuce has very low nutritional content. It just a cop out for restaurants.
Why would it be just filler? You're probably not eating enough. It has high fiber content, just like most vegetables (and actually a very similar macro nutrient ratio)
This is misinformed. Iceberg lettuce contains very little fiber, either.
Lettuce is mostly water. Romani lettuce is a bit better but still bad. Out of leafy greens: spinach, beet greens, nettle, rucola and cabbages (everything Brassica spp.)- are decent nutritionally, a few others in small doses too.
100%. My go-to saying is “lettuce is for rabbits”. And I opt out of lettuce on anything I can.