Thin-sliced meats also allow you to create a neat, stable, structurally sound base that's less likely to fall apart when you stack on other ingredients to fill out your sandwich.
Using thinner slices also means there’s more room for different kinds of meat while still keeping the sandwich manageable. You can interlace these slices to weave together flavors.
Thin-sliced deli meat's delicate texture and thinness will enhance your sandwich and give it a more pronounced flavor. It will also make it easier to warm up.