The same thing is happening with me and I don't understand how to fix it.
- Open the folder with WickedWhims files.
- Place the TURBODRIVER_CAS_DefaultUnderwear.package file inside the folder with other WickedWhims files.
- Make sure the TURBODRIVER_CAS_DefaultUnderwear file is in alphabetical order before the TURBODRIVER_WickedWhims_Tuning file.
If Sims are still naked in CAS, the TURBODRIVER_CAS_DefaultUnderwear file is being loaded after WickedWhims or you have other mods that make Sims naked in CAS.
(Even though this info didn't help me it may always help you) this was direct info from the cas default underwear download screen and even though my files are put in correctly and I have nothing else that would make them naked, it still is doing so. I completely took out everything I had that had to do with the mod and it was still happening.