when we say XYZ brands do handmade bags, its good to remember that not ALL bags by these brands are made by hand, and very, very few are 100% handmade. Often some elements are handmade, for example in an Hermes Birkin the handles are handmade as is the top edge part of the bag. All the rest of the bag is machine stitched.
Joseph Duclos has a bag that 100% hand stitched - the Saint Clair, which is a little beauty & very special because its really a different type of make, not a regular saddle stitch. Their other models have some elements that are hand stitched like the handles.
as for Delvaux, some of their special « leather mastery » collection have some hand made elements, but not their regular collection. Plus the special bags are not 100% hand made.
We will all grow old waiting for Chanel to do handmade bags
But like you said, why should they when clients are happy to pay premium €$ the way it is !