When running NM cable, you're supposed to not make any bends sharper than 5 times the cable radius.*
When dressing wires to go into a box, though, you often curve them any which way or shape them into an accordion to leave a workable length while fitting them behind the device fixed to the front of the box.
Why be concerned about how sharply the wires are bent in one case but not the other?
(Regardless of the answer, Code demands conformance. This is purely curiosity.)
* Or something like that - I just remember the rule that for 14 or 12 gauge you want to go no sharper than the bend in a soda can. When I run thicker cable, I'll look up the details then.