For a 1950's style dress would you sew the underskirt in?

[KatyMac]

Or have it separate?

I'm leaning towards having it sewn in, but I don't know why as if I were buying one I already have an underskirt

I am illogical

I think separate as it would be a nightmare to wash wouldn't it?

yes - except I have a tea dress from Pepperberry where it's fixed in and the waist is very neat