The category of clothing worn to American offices changed substantially over the last two decades. Several separate developments pushed in the same direction at once.
Fabric technology arrived before the trend
Performance textiles developed for athletic use brought stretch, moisture management and wrinkle resistance into garments that could be produced at scale.
Those properties solve ordinary problems: comfort through a long day, tolerance of a commute, and looking acceptable without pressing.
Once the fabrics existed, applying them to trousers, blazers and dresses was a straightforward step, and the resulting garments competed directly with traditional tailoring on comfort.
Office dress codes had already been loosening
Formality in American workplaces declined steadily, first through casual days, then through technology sector norms that spread into other industries.
As the floor moved, the reference point for appropriate dress moved with it, and each shift made the next one less remarkable.
Remote and hybrid work accelerated this by removing daily observation, which is the mechanism that had enforced the previous standard.
Wardrobe economics favor versatile garments
Clothing that works for the office, errands and social plans reduces the number of garments a person needs and the mental cost of choosing between them.
A traditional suit is single-purpose, expensive per wear if the purpose is infrequent, and requires professional cleaning that adds ongoing cost.
Versatile pieces get worn more often, which changes the calculation in their favor even at similar purchase prices.
Retailers found the category easier to sell
Stretch-based garments fit a wider range of body dimensions than structured tailoring, which reduces size fragmentation and lowers return rates.
Fewer sizes needed per style means less inventory risk, and lower returns matter enormously in online retail where returns are a major cost.
Those advantages made the category attractive to sell, which increased how much of it was produced, marketed and placed in front of buyers.
The shift has costs that are less discussed
Structured tailoring communicates authority in certain settings, and the norms for what reads as appropriately senior have not shifted evenly across industries.
Ambiguous dress codes place the interpretive burden on the employee, and judgments about appropriateness continue to be applied unevenly by gender.
Most performance fabrics are also synthetic, which affects durability, laundering behavior and end-of-life disposal in ways that natural fibers do not share.