In the same way as the sportswear revolution was responsible for deconstructing corsets, fashion movements of the 1920’s were sparked by social situations. Trousers had come in through the back door. (1)
If it had become acceptable for modern Frenchwomen to wear pants for sports, French fashion magazines, and by inference their readers, did not considered tailored pants suitable for ladies to wear on city or in public. (2)
Trousers as we see them today, never really became part of the 1920’s women’s attire.
Not one article on wardrobes included city pants, and only a few articles on vacation attire included slacks of any kind. In the 1940’s, it was still unusual for stylish women to wear pants in cities. (2)
Although you can still find some exceptions in 1920’s pictures of brave women who adopted men’s trousers as their own. Mostly still, had been worn at sports related events or indoors.
(1) Vogue Fashion – Linda Watson, 2008
(2) Dressing Modern Frenchwomen: Marketing Haute Couture, 1919-1939 – Mary Lynn Stewart, 2008