Why is the lining of your mouth stratified but the lining of your small intestine is not?

The lining of your mouth is stratified but the lining of your small intestine is not because the primary function of the stratified lining is to protect the body when it comes to close contact to the outside environment.

The mouth has stratified squamous epithelia. This epithelia serves as protection of the mouth from mechanical or chemical abrasion, stress, desiccation, and water loss.

The lining of the small intestine is not stratified because it has a different purpose. It is folded back and forth. This is to ensure that the small intestine has a larger surface area that can absorb nutrients.