Why is lettuce rarely cooked? Most, if not all, of the lettuce I've seen has been uncooked, usually as a salad, wrap, or garnish. I don't recall ever seeing it being heated, even though visually similar leafy vegetables, like cabbage or kale, are often cooked. I have a feeling that this has something to do with the lettuce's water content, but that's just idle speculation.

Why isn't lettuce usually heated as part of the cooking process? I'm mainly looking for what happens when it is cooked that discourages people from cooking it, but I'd also like to know the scientific explanation. Instances of successful lettuce-cooking, if such exist, would be welcome, as well as explanations about what makes the cooking work in that particular situation.
Cooking lettuce is not as unusual as you think. It's kind of trendy to grill romaine,



and iceberg lettuce is often cooked in Chinese cuisine, both in soups and stir-fries.





There is a recipe for braised lettuce in Julia Child's Mastering the Art of French Cooking,



and Lidia Bastianich, who specializes in Italian cuisine, recently did a stuffed and cooked lettuce (escarole) on her show.