For me it was the other way around. I always used a belt and felt like my body was relying on it too much. Ive deadlifted 495 with no belt and just chalk and my core felt the best it ever had.
use it whenever i go above 3 plates on squat or DL. no point in fuckin up my back for a lil extra core work. but those are usually the last 1 or 2 sets.