Melamine cabinets typically are whitened with no ornamental touches or much visual appeal. Wallpaper can add those things, and is not as cluttered or as inclined to chipping and peeling as paint.
You can put wallpaper over melamine cupboards as long as the surface is properly prepared. The cupboard face has to be washed to remove any grease or dust that would make it difficult for the background to adhere. Any chips or damage should be repaired since any irregular spots are very likely to show through the background. The borders of the wallpaper may need to be safeguarded by adding decorative wood trim if the doors are wholly flat and plain. You can also use clear plastic corner guards to prevent the wallpaper from curling or being damaged at the borders if the cabinet doors don’t have trim.