What happens if you don't put clear coat on paint?

If you don't put clear coat on paint, consequences depend on type of paint system. For automotive painting, base coat color is not durable alone, it is matte and has no UV protection or gloss, so without clear coat, color will fade quickly from sun, will have dull flat appearance, will be easily scratched, chipped by stones, and damaged by weather, chemicals, and washing, and will not have glossy showroom shine, so clear coat is essential for gloss and protection. For house paint, clear coat is not typically used, as topcoat paint itself contains resins for protection, so skipping clear coat is normal. For wood furniture painted with color paint, if you don't put clear top coat like polyurethane over paint, paint may still be okay if it is high quality enamel, but will be less resistant to scratches, water, and wear, especially for high use surfaces like tables and cabinets. For art and crafts, without clear coat, paint may be less protected from dust and UV and may fade. For nail polish, without clear top coat, color chips faster and has less shine. So for car base coat, not putting clear coat results in dull, unprotected, quickly fading finish, while for house walls, clear coat not needed as topcoat paint itself is protective, but for wood and art, skipping clear reduces durability.