Natures do not affect IV generation during breeding*. IV generation is random* (and so are the IVs picked out by Destiny Knot). You are simply having bad luck, so keep hatching Bounsweet and you will eventually get one with a high Attack IV.
If one or both of Steenee and Comfey has a high Attack IV that you're trying to pass down, then you may find Power Bracer helpful. The Pokemon that holds it will pass down its Attack IV 100% of the time.
* subject to the properties of Pokemon's RNG, but you don't need to worry about that