Blue Jeans on Subway

So I’m watching I Love Lucy – it’s the episode where she gets her head stuck in a trophy.

Ethel – her best friend – decides to take her to the silversmith so he can cut it off and they decide the subway would be faster than a taxi. (Considering city traffic, they could be right.)

And Ethel refuses to wear her blue jeans on the subway. She goes and comes back in a dress.

What is up with that? Was there really a time when wearing jeans on the subway was weird?