A wrap is a sandwich but a lettuce wrap is NOT a sandwich for two crucial reasons:
1) it is not filling between two pieces of bread. The bread is key.
2) lettuce wilts, breaks, and is easily torn, making it a less-than-ideal material for a wrap. Therefore, it is particularly ill-suited to enabling the wretched gambling habits of the regency by allowing them to eat with one hand and throw dice with the other. Therefore it does not earn the name of the Earl of Sandwich, who commissioned the sandwich for just that reason.
1) The verb ‘sandwich’ means to insert or squeeze something between two other things. If you are sandwiching lettuce between lettuce, what you have is a sandwich!
2) Boston, Bibb, and Butter lettuce is quite sturdy and makes an ideal sandwich wrap!