AFAIK the norm is that the row in front of an exit row doesn't recline, which would include the first exit row on many DL aircraft configurations. The rationale is that if the seat in front of an exit row is reclined, this impedes evacuation in an emergency. However, the second (or last) exit row IME does recline. YMMV of course as this is DL.

OTOH <joke> maybe DL wants people seated in exit rows to stay wide awake, and being able to recline would facilitate or enable naps on board. By the same reasoning, there should be special nonreclining seats for FAMs.