From my readings there are two types: a wet sticky chick which denotes high humidity during incubation resulting in not enough moisture escaping the egg and a dry sticky chick which is the result of too low humidity during hatch or a sudden drop of humidity during hatch which quickly dries the moisture causing the stickiness.
I didn't contribute it to the second one because usually (in my mind...yes, a scary place,) those are the ones that the membrane starts turning a yellowish brown and they need assistance to get unstuck just to finish and then you know that's what's going on.