<p>Because Likely Letters increase attachment to a school which then leads to a higher yield among LL recipients. Duke doesn’t need a higher yield among white/ORM applicants, but their URM population could use some bolstering. Thus, they send out LLs to URMs in hopes of further diversifying their student body.</p>
<p>Btw, I pulled this explanation completely out of my ass but it seems like it makes sense.</p>