If you have a Traversable instance of a record, you can load and store all elements, that are accessible by Traversable methods. We treat the record like an array, that is we assume, that all elements have the same size and alignment.

Example:

 import Foreign.Storable.Traversable as Store

 data Stereo a = Stereo {left, right :: a}

 instance Functor Stereo where
    fmap = Trav.fmapDefault

 instance Foldable Stereo where
    foldMap = Trav.foldMapDefault

 instance Traversable Stereo where
    sequenceA ~(Stereo l r) = liftA2 Stereo l r

 instance (Storable a) => Storable (Stereo a) where
    sizeOf = Store.sizeOf
    alignment = Store.alignment
    peek = Store.peek (error "instance Traversable Stereo is lazy, so we do not provide a real value here")
    poke = Store.poke

You would certainly not define the Traversable and according instances just for the implementation of the Storable instance, but there are usually similar applications where the Traversable instance is useful.