How often do most people wear evening gowns and tuxes nowadays in the US? Less and less often, for certain in New England, as even the upper classes and aristocracy prefer more informal events and dress.
Where the instructions "Formal attire" used to mean gowns and dinner dress fro men, now it means dresses and suits. Dress has obviously become small-d democratized. There is a loss in that, a loss of elegance at the least.
We're now at the point where even formal black or white-tie weddings (evenings only, please) look like silly costume shows. That ten year-old gown should be fine, and who cares?
I recently realized that I own enough formal wear, footwear, outerwear, sportswear, riding wear, ski gear, boating gear, and athletic gear to last my lifetime, not including new tennis racquets. I am done accumulating it as long as my size doesn't change, which will not.