Oh Good: Cooking Sprays Are Probably Ruining Your Nonstick Pans
You can't necessarily see that residue, because nonstick coatings are all black, but if you don't properly clean it off after you're done cooking, then your food will start to stick.
Julia Child's Pro Advice That Ensures Your Omelets Never Stick To The Pan - Tasting Table
Season an iron or steel pan, heat it and add oil overnight, then use a hot, well-seasoned (or good nonstick) pan with up to three eggs for a French omelet.