The higher the quality of the item, the more likely it is to employ materials that cannot be machine-washed.
Formal clothes are usually made from fabrics that must be dry-cleaned rather than machine-washed, which increases the overall cost of the garment.
Even shorts that can be machine-washed will do better if they are washed by hand, or at least hang-dried.
All Wigwam socks can be machine-washed and dried quickly.
Cotton bras can usually be machine-washed and tend to last much longer than fancier bras with radical embellishments.