A simple black dress has remained a fixture across a century of otherwise complete change in womenswear. Its durability comes from specific properties of the colour and the form rather than from sentiment.
Black conceals the things a dress reveals
A saturated black surface reflects very little light, so the shadows that normally describe a garment's shape are flattened.
Seams, darts, gathers and any slight irregularity in construction become far harder to read, which is why black is forgiving of both the body and the making.
The same property means a black dress photographs as a silhouette rather than as a set of details, which has kept it usable as visual fashion changed around it.
It sits inside almost every dress code
Dress codes tend to specify what is too casual and what is too elaborate, and a plain dark dress avoids both boundaries at once.
That makes it acceptable across a very wide range of occasions, from work to evening events, without appearing to have been chosen for any one of them.
A garment that can be worn in many contexts earns far more wears than one tied to a single occasion, which is the practical case for owning it.
Accessories carry the seasonal work
Because the dress itself is neutral, everything visible alongside it, from shoes and jewellery to outerwear, determines how it is read.
Changing those items changes the outfit completely while the dress remains the same, so it does not date at the rate the accessories do.
This is also commercially convenient, since accessories are cheaper to buy and replace than the garment they are being used to update.
Simplicity survives changes in silhouette
The form is not fixed. Length, neckline, sleeve and waist placement have all moved substantially across decades.
What persists is the principle of a single unbroken dark garment with minimal ornament, which can be recut to whatever proportion is current.
A heavily decorated dress cannot be updated in the same way, because its decoration ties it to the moment it was designed.
Black also solves a maintenance problem
Dark fabric hides marks and wear that would be visible on a pale garment, extending how long an item looks presentable between cleanings.
It does fade with washing and light exposure, and a faded black reads as tired in a way a faded colour does not, so care matters more than it appears to.
That trade-off is why quality of dye and fibre shows up so clearly in black clothing, and why two apparently identical dresses can diverge sharply after a year of wear.